Production of fibrinolytic enzyme from Bacillus amyloliquefaciens by fermentation of chickpeas, with the evaluation of the anticoagulant and antioxidant properties of chickpeas

Phenotypic and genomic insights into mutant with high nattokinase-producing activity induced by carbon ion beam irradiation of Bacillus subtilis

Nattokinase (NK) is found in fermented foods and has high fibrinolytic activity, which makes it promising for biological applications. In this study, a mutant strain (Bacillus subtilis ZT-S1, 5529.56 ± 183.59 U/mL) with high NK-producing activity was obtained using 12C6+ heavy ion beam mutagenesis for the first time. The surface morphology of B. subtilis is also altered by changes in functional groups caused by heavy ion beams. Furthermore, B. subtilis ZT-S1 required more carbon and nitrogen sources and reached stabilization phase later. Comparative genome analysis revealed that most of the mutant implicated genes (oppA, appA, kinA, spoIIP) were related to spore formation. And the affected rpoA is related to the synthesis of the NK-coding gene aprE. In addition, the B. subtilis ZT-S1 obtained by mutagenesis had good genetic stability. This study further explores the factors affecting NK activity and provides a promising microbial resource for NK production in commercial applications.

A smart RBS library and its prediction model for robust and accurate fine-tuning of gene expression in Bacillus species

Bacillus species, such as Bacillus subtilis and Bacillus licheniformis, are important industrial bacteria. However, there is a lack of standardized and predictable genetic tools for convenient and reproducible assembly of genetic modules in Bacillus species to realize their full potential. In this study, we constructed a Ribosome Binding Site (RBS) library in B. licheniformis, which provides incremental regulation of expression levels over a 104-fold range. Additionally, we developed a model to quantify the resulting translation rates. We successfully demonstrated the robust expression of various target genes using the RBS library and showed that the model accurately predicts the translation rates of arbitrary coding genes. Importantly, we also extended the use of the RBS library and prediction model to B. subtilis, B. thuringiensis, and B. amyloliquefacie. The versatility of the RBS library and its prediction model enables quantification of biological behavior, facilitating reliable forward engineering of gene expression.

Modeling and in-vivo evaluation of fibrinolytic enzyme produced by Bacillus subtilis Egy under solid state fermentation

Blood clot formation increases cases of myocardial infarction (AMI) and stroke, thus urges directing much research works for treatment and prevention of the causes. One of these directions is the microbial production of fibrinolytic enzymes as thrombolytic agents. In the current work, Bacillus subtilis Egy has been used for enzyme production under solid state fermentation. Among twelve nutrient meals in addition to wheat bran as a control fodder yeast yielded the highest enzyme activity reaching 114U/g. Applying statistical model for optimization of enzyme production revealed that 3.6%, fodder yeast; 40%, moisture content; 6 days, incubation period and 2%, inoculum size were the optimum conditions for maximum fibrinolytic enzyme production (141.02 U/g) by Bacillus subtilis Egy under solid-state fermentation The model was significant and data were experimentally validated. The produced fibrinolytic enzyme was evaluated for in vitro and in vivo cytotoxicity. In-vivo examination of the enzyme resulted in no mortality during the first 24 h after treatment. After 14 days, the results revealed no significant changes detected in hematological parameters (RBCs, MCV, hemoglobin except WBCs which showed an increase for both sexes. Histopathological examination of liver and kidney of rats received oral and subcutaneous treatments showed normal architecture. The data showed the applicability of the produced enzyme for the treatment of blood clot with no significant effect on living cells or on physiological functions.

Microbial nattokinase: from synthesis to potential application

Nattokinase (NK) is an alkaline serine protease with strong thrombolytic activity produced by Bacillus spp. or Pseudomonas spp. It is a potential therapeutic agent for thrombotic diseases because of its safety, economy, and lack of side effects. Herein, a comprehensive summary and analysis of the reports surrounding NK were presented, and the physical-chemical properties and producers of NK were first described. The process and mechanism of NK synthesis were summarized, but these are vague and not specific enough. Further results may be achieved if detection techniques such as multi-omics are used to explore the process of NK synthesis. The purification of NK has problems such as a complicated operation and low recovery rate, which were found when summarizing the techniques to improve the quality of finished products. If multiple simple and efficient precipitation methods and purification materials are combined to purify NK, it may be possible to solve the current challenges. Additionally, the application potential of NK in biomedicine was reviewed, but functional foods with NK are challenging for acceptance in daily life due to their unpleasant odor. Accordingly, multi-strain combination fermentation or food flavoring agents can improve the odor of fermented foods and increase people's acceptance of them. Finally, the possible future directions focused on NK studies were proposed and provided suggestions for subsequent researchers.

Production, purification, and functional properties of microbial fibrinolytic enzymes produced by microorganism obtained from soy-based fermented foods: developments and challenges

According to the World Health Organization, cardiovascular disease (CVD) has become a major cause of chronic illness around the globe. It has been reported that soy-based fermented food (SFF) is very effective in preventing thrombus (one of the most important contributing factors to CVD), which are mainly attributed to the bioactive substances, especially the fibrinolytic enzymes (FE) generated by microorganisms during the fermentation process of soybean food. This paper therefore mainly reviewed the microbial fibrinolytic enzymes (MFE) from SFF. We first discuss the use of microbial fermentation to produce FE, with an emphasis on the strains involved. The production, purification, physicochemical properties, structure-functional attributes, functional properties and possible application of MFE from SFF are then discussed. Finally, current limitations and future perspectives for the production, purification, and the practical application of MFE are discussed. MFE from SFF pose multiple health benefits, including thrombolysis, antihypertension, anti-inflammatory, anti-hyperlipidemia, anticancer, neuroprotective, antiviral and other activities. Therefore, they exhibit great potential for functional foods and nutraceutical applications, especially foods with CVDs prevention potential.

Genetic engineering for enhanced production of a novel alkaline protease BSP-1 in Bacillus amyloliquefaciens

Alkaline protease has been widely applied in food, medicine, environmental protection and other industrial fields. However, the current activity and yield of alkaline protease cannot meet the demand. Therefore, it is important to identify new alkaline proteases with high activity. In this study, we cloned a potential alkaline protease gene bsp-1 from a Bacillus subtilis strain isolated in our laboratory. BSP-1 shows the highest sequence similarity to subtilisin NAT (S51909) from B. subtilis natto. Then, we expressed BSP-1 in Bacillus amyloliquefaciens BAX-9 and analyzed the protein expression level under a collection of promoters. The results show that the P43 promoter resulted in the highest transcription level, protein level and enzyme activity. Finally, we obtained a maximum activity of 524.12 U/mL using the P43 promoter after fermentation medium optimization. In conclusion, this study identified an alkaline protease gene bsp-1 from B. subtilis and provided a new method for high-efficiency alkaline protease expression in B. amyloliquefaciens.

Characterization of a Nattokinase from the Newly Isolated Bile Salt-Resistant Bacillus mojavensis LY-06

Nattokinase is a potential new thrombolytic drug because of its strong thrombolytic effect, high safety, and low cost. However, there is no research reporting on bile salt-tolerant nattokinase-producing probiotics. In this study, the bile salt-tolerant nattokinase-producing strain Bacillus mojavensis LY-06 was isolated from local Xinjiang douchi, and the fermentation yield of nattokinase of 1434.64 U/mL was obtained by both a single factor experiment and an orthogonal experiment. A gene responsible for fibrinolysis (aprY) was cloned from the genome of strain Bacillus mojavensis LY-06, and the soluble expression of this gene in Escherichia coli (rAprY, fused with His-tag at C-terminus) was achieved; molecular docking elucidates the cause of insoluble expression of rAprY. The optimal pH and temperature for the fibrinolysis activity of nattokinase AprY fermented by Bacillus mojavensis LY-06 were determined to be pH 6.0 and 50 °C, respectively. However, the optimal pH of rAprY expressed in Escherichia coli was 8, and its acid stability, thermal stability, and fibrinolytic activity were lower than those of AprY. Bioinformatics analysis found that the His-tag carried at the C-terminus of rAprY could affect its acidic stability by changing the isoelectric point and surface charge of the enzyme; in contrast to AprY, changes in the number of internal hydrogen bonds and the flexibility of the loop region in the structure of rAprY resulted in lower fibrinolytic activity and poorer thermal stability.

Fermented soybean foods: A review of their functional components, mechanism of action and factors influencing their health benefits

After thousands of years of evolution and development, traditional fermented soybean foods, with their unique charm, have gained a stable place in the global market. With the explosive development of modern biological technologies, some traditional fermented soybean foods that possess health-promoting benefits are gradually appearing. Physiologically active substances in fermented soybean foods have received extensive attention in recent decades. This review addresses the potential health benefits of several representative fermented soybean foods, as well as the action mechanism and influencing factors of their functional components. Phenolic compounds, low-molecular-weight peptides, melanoidins, furanones and 3-hydroxyanthranilic acid are the antioxidative components predominantly found in fermented soybean foods. Angiotensin I-converting enzyme inhibitory peptides and γ-aminobutyric acid isolated from fermented soy foods provide potential selectivity for hypertension therapy. The potential anti-inflammatory bioactive components in fermented soybean foods include γ-linolenic acid, butyric acid, soy sauce polysaccharides, 2S albumin and isoflavone glycones. Deoxynojirimycin, genistein, and betaine possess high activity against α-glucosidase. Additionally, fermented soybean foods contain neuroprotective constituents, including indole alkaloids, nattokinase, arbutin, and isoflavone vitamin B12. The anticancer activities of fermented soybean foods are associated with surfactin, isolavone, furanones, trypsin inhibitors, and 3-hydroxyanthranilic acid. Nattokinase is highly correlated with antioxidant activity. And a high level of menaquinones-7 is linked to protection against neurodegenerative diseases. Sufficiently recognizing and exploiting the health benefits and functional components of traditional fermented soybean foods could provide a new strategy in the development of the food fermentation industry.

Biotechnology, Bioengineering and Applications of Bacillus Nattokinase

Thrombosis has threatened human health in past decades. Bacillus nattokinase is a potential low-cost thrombolytic drug without side-effects and has been introduced into the consumer market as a functional food or dietary supplement. This review firstly summarizes the biodiversity of sources and the fermentation process of nattokinase, and systematically elucidates the structure, catalytic mechanism and enzymatic properties of nattokinase. In view of the problems of low fermentation yield, insufficient activity and stability of nattokinase, this review discusses the heterologous expression of nattokinase in different microbial hosts and summarizes the protein and genetic engineering progress of nattokinase-producing strains. Finally, this review summarizes the clinical applications of nattokinase.

Recent Advances in Nattokinase-Enriched Fermented Soybean Foods: A Review

With the dramatic increase in mortality of cardiovascular diseases (CVDs) caused by thrombus, this has sparked an interest in seeking more effective thrombolytic drugs or dietary nutriments. The dietary consumption of natto, a traditional Bacillus-fermented food (BFF), can reduce the risk of CVDs. Nattokinase (NK), a natural, safe, efficient and cost-effective thrombolytic enzyme, is the most bioactive ingredient in natto. NK has progressively been considered to have potentially beneficial cardiovascular effects. Microbial synthesis is a cost-effective method of producing NK. Bacillus spp. are the main production strains. While microbial synthesis of NK has been thoroughly explored, NK yield, activity and stability are the critical restrictions. Multiple optimization strategies are an attempt to tackle the current problems to meet commercial demands. We focus on the recent advances in NK, including fermented soybean foods, production strains, optimization strategies, extraction and purification, activity maintenance, biological functions, and safety assessment of NK. In addition, this review systematically discussed the challenges and prospects of NK in actual application. Due to the continuous exploration and rapid progress of NK, NK is expected to be a natural future alternative to CVDs.

Novel green soybean shuidouchi fermented by Bacillus velezensis with multibioactivities

Soybeans are usually fermented by Bacillus subtilis to produce shuidouchi, which is a traditional fermentation soybean product in China. In the study, green soybeans were fermented by Bacillus velezensis to make a novel green soybean shuidouchi with multibioactivities. The processing conditions were optimized as follows: initial moisture content 75%, inoculum concentration 7 log CFU/g, and incubation time 24 h for prefermentation; water addition 50%, salt addition 6%, temperature 45°C, 3 days for postfermentation. The fermented green soybean shuidouchi (FGSS) showed 234.8 FU/g dry weight (DW) for the fibrinolytic activity and IC50 of 0.33 mg/ml for the anticoagulant activity. FGSS had higher contents of chemical components including 3.6 mg rutin (RE)/g DW of total flavonoids, 8.2 mg gallic acid (GAE)/g DW of total phenolics, 63.7 mg/g DW of reducing sugars, and 163.8 mg/g DW of peptides than the unfermented green soybean shuidouchi (UGSS). Moreover, it exhibited high antioxidant activities of 29.8, 85.1 μmol trolox equivalent (TE)/g DW, and 12.8 μmol Fe2+/g DW through 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS), and ferric reducing antioxidant power (FRAP) experiments. Thus, a novel green soybean shuidouchi fermented by B. velezensis owing to multibioactivities can provide a theoretical basis for the further development of functional shuidouchi.

Microbial Fibrinolytic Enzymes as Anti-Thrombotics: Production, Characterisation and Prodigious Biopharmaceutical Applications

Cardiac disorders such as acute myocardial infarction, embolism and stroke are primarily attributed to excessive fibrin accumulation in the blood vessels, usually consequential in thrombosis. Numerous methodologies including the use of anti-coagulants, anti-platelet drugs, surgical operations and fibrinolytic enzymes are employed for the dissolution of fibrin clots and hence ameliorate thrombosis. Microbial fibrinolytic enzymes have attracted much more attention in the management of cardiovascular disorders than typical anti-thrombotic strategies because of the undesirable after-effects and high expense of the latter. Fibrinolytic enzymes such as plasminogen activators and plasmin-like proteins hydrolyse thrombi with high efficacy with no significant after-effects and can be cost effectively produced on a large scale with a short generation time. However, the hunt for novel fibrinolytic enzymes necessitates complex purification stages, physiochemical and structural-functional attributes, which provide an insight into their mechanism of action. Besides, strain improvement and molecular technologies such as cloning, overexpression and the construction of genetically modified strains for the enhanced production of fibrinolytic enzymes significantly improve their thrombolytic potential. In addition, the unconventional applicability of some fibrinolytic enzymes paves their way for protein hydrolysis in addition to fibrin/thrombi, blood pressure regulation, anti-microbials, detergent additives for blood stain removal, preventing dental caries, anti-inflammatory and mucolytic expectorant agents. Therefore, this review article encompasses the production, biochemical/structure-function properties, thrombolytic potential and other surplus applications of microbial fibrinolytic enzymes.

Role of Fibrinolytic Enzymes in Anti-Thrombosis Therapy

Thrombosis, a major cause of deaths in this modern era responsible for 31% of all global deaths reported by WHO in 2017, is due to the aggregation of fibrin in blood vessels which leads to myocardial infarction or other cardiovascular diseases (CVDs). Classical agents such as anti-platelet, anti-coagulant drugs or other enzymes used for thrombosis treatment at present could leads to unwanted side effects including bleeding complication, hemorrhage and allergy. Furthermore, their high cost is a burden for patients, especially for those from low and middle-income countries. Hence, there is an urgent need to develop novel and low-cost drugs for thrombosis treatment. Fibrinolytic enzymes, including plasmin like proteins such as proteases, nattokinase, and lumbrokinase, as well as plasminogen activators such as urokinase plasminogen activator, and tissue-type plasminogen activator, could eliminate thrombi with high efficacy rate and do not have significant drawbacks by directly degrading the fibrin. Furthermore, they could be produced with high-yield and in a cost-effective manner from microorganisms as well as other sources. Hence, they have been considered as potential compounds for thrombosis therapy. Herein, we will discuss about natural mechanism of fibrinolysis and thrombus formation, the production of fibrinolytic enzymes from different sources and their application as drugs for thrombosis therapy.

Antioxidant Properties and Diet-Related α-Glucosidase and Lipase Inhibitory Activities of Yogurt Supplemented with Safflower (Carthamus tinctorius L.) Petal Extract

Recently, yogurt has been extensively studied to further enhance its functions using edible plant extracts. This study was conducted to investigate whether safflower petal (SP) as a natural food additive can be used to develop functional yogurt with improved health benefits. SPs were extracted with ethanol (SPE) and hot water (SPW), and then safflower yogurt was prepared by adding 0%-1.0% of those extracts to plain yogurt. With an increase in the fermentation duration, the pH of SPE and SPW yogurt samples was decreased, whereas titratable acidity and microbial counts were increased. The concentration of total polyphenols and total flavonoids, the activity of antioxidants, and the inhibitory effect on reactive oxygen species (ROS) were higher in SPW yogurt than SPE yogurt. Furthermore, α-glucosidase and lipase activity inhibitory effects of SPW yogurt were higher than those of SPE yogurt. In particular, free radical-scavenging activities, ROS inhibitory effect, and α-glucosidase activity inhibitory effects were significantly increased in SPW yogurt in a dose-dependent manner. Overall, these results suggest that SP extract possesses antioxidant activities and that it can downregulate α-glucosidase and lipase activities. The SP extract may have potential benefits as a natural food additive for the development of functional yogurt.

Protective Effects of Fermented Paprika (Capsicum annuum L.) on Sodium Iodate-Induced Retinal Damage

Diseases of the outer retina, including age-related macular degeneration (AMD), are major cause of permanent visual damage. The pathogenesis of AMD involves oxidative stress and damage of the retinal pigment epithelium. Capsicum annuum L. (paprika) fruits have been known as a source of vitamins, carotenoids, phenolic compounds, and metabolites with a well-known antioxidant activity, which have positive effects on human health and protection against AMD and cataracts. In this study, we investigated whether paprika (fermented (FP), yellow, and orange colored) fermented with Lactobacillus (L.) plantarum could increase the protective effect of retinal degeneration using in vitro and in vivo models. FP significantly increased cell survival and reduced levels of lactate dehydrogenase as well as intracellular reactive oxygen species (ROS) increase in SI (sodium iodate, NaIO₃)-treated human retinal pigment epithelial (ARPE-19) cells. We developed a model of retinal damage in C57BL/6 mice using SI (30 mg/kg) via intraperitoneal injection. Seven days after SI administration, deformation and a decrease in thickness were observed in the outer nuclear layer, but improved by FP treatment. FP administration protected the SI-mediated reduction of superoxide dismutase and glutathione levels in the serum and ocular tissues of mice. The overproduction of cleaved poly(ADP-Ribose) Polymerase (PARP)1, caspase-3 and -8 proteins were significantly protected by FP in SI-treated cells and ocular tissues. In addition, we evaluated the potentiating effects of FP on antioxidants and their underlying mechanisms in RAW 264.7 cells. Lipopolysaccharide (LPS)-induced nitrite increase was markedly blocked by FP treatment in RAW 264.7 cells. Furthermore, FP reduced LPS-induced inducible nitric oxide synthase and cyclooxygenase-2 activation. The FP also enhanced the inhibitory effects on mitogen activated kinase signaling protein activation in ARPE-19 and RAW 264.7 cells and ocular tissues. There was no significant difference in total phenol and flavonoid content in paprika by fermentation, but the vitamin C content was increased in orange colored paprika, and protective effect against oxidative stress-mediated retinal damage was enhanced after fermentation. These results suggest that FP may be a potential candidate to protect against retinal degenerative diseases through the regulation of oxidative stress.

Purification, physicochemical properties, and statistical optimization of fibrinolytic enzymes especially from fermented foods: A comprehensive review

Fibrinolytic enzymes are proteases responsible for cleavage of fibrin mesh in thrombus clots, which are the primary causative agents in cardiovascular diseases. Developing safe, effective and cheap thrombolytic agents are important for prevention and cure of thrombosis. Although a wide variety of sources have been discovered for fibrinolytic enzymes, only few of them have been employed in clinical and therapeutic applications due to the drawbacks such as high cost of production, low stability of enzyme or therapeutic side effects. However, the discovery of new fibrinolytic enzymes requires complex purification stages and characterization, which gives an insight into their diverse modes of action. Post-discovery, approaches such as a) statistical optimization for fermentative bioprocessing and b) genetic engineering are advantageous in providing economic viability by finding simple and cost-effective medium, strain development with sufficient nutrient supplements for stable and high-level production of recombinant enzyme. This review provides a comprehensive understanding of different sources, purification techniques, production through genetic engineering approaches and statistical optimization of fermentation parameters as proteases have a wide variety of industrial and biotechnological applications making 60% of total enzyme market worldwide. New strategies targeting increased enzyme yields, non-denaturing environments, improved stability, enzyme activity and strain improvement have been discussed.

Molecular analysis of a fibrin-degrading enzyme from Bacillus subtilis K2 isolated from the Indonesian soybean-based fermented food moromi

The screening of proteolytic and fibrinolytic bacteria from moromi (an Indonesian soybean-based fermented food) yielded a number of isolates. Based on morphological and biochemical analyses and sequencing of the 16S rRNA gene, the isolate that exhibited the highest proteolytic and fibrinolytic activity was identified as Bacillus subtilis K2. The study was performed to analyze molecular characteristic of a fibrin-degrading enzyme from B. subtilis K2. BLASTn analysis of the nucleotide sequence encoding this fibrinolytic protein demonstrated 73.6% homology with the gene encoding the fibrin-degrading enzyme nattokinase of the B. subtilis subsp. natto, which was isolated from fermented soybean in Japan. An analysis of the putative amino-acid sequence of this protein indicated that it is a serine protease enzyme with aspartate, histidine, and serine in the catalytic triad. This enzyme was determined to be a 26-kDa molecule, as confirmed with a zymogram assay. Further bioinformatic analysis using Protparam demonstrated that the enzyme has a pI of 6.02, low instability index, high aliphatic index, and low GRAVY value. Molecular docking analysis using HADDOCK indicated that there are favorable interactions between subtilisin K2 and the fibrin substrate, as demonstrated by a high binding affinity (ΔG: - 19.4 kcal/mol) and low Kd value (6.3E-15 M). Overall, the study concluded that subtilisin K2 belong to serine protease enzyme has strong interactions with its fibrin substrate and fibrin can be rapidly degraded by this enzyme, suggesting its application as a treatment for thrombus diseases.

Effects of Lotus (Nelumbo nucifera) Leaf Hot Water Extracts on the Quality and Stability of Eggs using Ultrasonication Treatment during Storage

This study was performed to investigate the effects of lotus leaf hot water extracts treatment on the quality and stability of eggs using impregnation treatment through ultrasonication during storage. A total of 480 eggs were categorized into four treatment groups (n=30 each)—non-treated (CON), soaked for 30 min in lotus leaf hot water extracts without ultrasonication (T1), sonicated in distilled water (T2), and sonicated in lotus leaf hot water extracts (T3)—and stored for 15 d at 30°C. The egg weight, Haugh unit (HU), egg grade, albumen height, yolk color, eggshell thickness, eggshell breaking strength, and weight loss were measured for egg quality assessment. 2-Thiobarbituric acid reactive substance (TBARS) and volatile basic nitrogen (VBN) contents were measured as stability indicators. Additionally, total phenolic contents (TPC), total flavonoid contents (TFC), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were evaluated. The HU, egg grade, albumen height, and yolk color of T3 were significantly higher than those of CON (p<0.05). No significant differences in eggshell thickness and eggshell breaking strength are observed among the groups. The weight loss of T3 was significantly lower than that of the other groups during storage (p<0.05). The application of lotus leaf hot water extracts also significantly reduced TBARS and VBN (p<0.05). The TPC, TFC, and DPPH radical scavenging activity of T3 were significantly higher than those of the other groups (p<0.05). These results suggest that lotus leaf hot water extracts may be useful as a natural ingredient for improving the quality and stability of eggs during storage.

Quality Characteristics and Antioxidant Activity of Yogurt Containing Raw Omija and Sugared Omija during Storage

This study was conducted to determine the quality characteristics and antioxidant properties of yogurt containing omija extract (control, raw omija, and sugared omija) stored at 4°C for 14 days. The pH of all groups decreased, while the titratable acidity increased as the storage period increased. The viscosity of the sugared omija sample was high, while in the syneresis test, the sugared omija sample showed a low value. The total polyphenol content was the highest in the raw omija sample on day 0. DPPH activity was the highest in the raw omija sample for all storage periods; this sample also showed high Fe2+ chelating activity, which did not significantly differ from the sugared omija sample. In sensory evaluation, the sugared omija sample showed the highest overall score. Based on these results, it can be concluded that yogurt containing sugared omija shows improved quality and antioxidant activity.

Biochemical and Antioxidant Activity of Yogurt Supplemented with Paprika Juice of Different Colors

Paprika is known to contain polyphenolic compounds that have good antioxidant properties. This study was conducted to investigate the benefits of adding paprika juice of different colors to yogurt and to determine how paprika affects the quality characteristics of yogurt. Stirred yogurt samples supplemented with different levels of red, orange, or yellow paprika juice were inoculated with mixes of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. Paprika addition decreased the pH but increased titratable acidity, lactic acid bacteria (LAB) counts, total polyphenol content (TPC), levels of vitamin A and C, and antioxidant activity. Proteolysis and viscosity of paprika-containing yogurts were significantly higher than those of the control yogurt without paprika juice (p<0.05). In particular, the viscosity of red paprika yogurt was significantly higher than that of yogurts containing 5% orange and yellow paprika juices (each p<0.05). The antioxidant activity of the methanol extract of the yogurt containing 2.5% orange paprika juice was the highest. Storage at 4°C for 15 days only slightly altered LAB counts, antioxidant activity, and TPC of paprika yogurt. These results indicate that paprika could be used as a natural food additive for the development of functional yogurts.

Molecular Characterization of Bacterial Fibrinolytic Proteins from Indonesian Traditional Fermented Foods

Previously, the crude extracts of recombinant Nattokinase (NK) variants i.e. NatTK and NatOC and one wild type Douchi Fibrinolytic Enzyme (DFE) from Indonesian traditional fermented foods has been shown to demonstrate fibrinolytic activity. Both NKs contain substitutions of D41N, V192A and 252-RLQHTLEALSTM-263 but NatOC has additional V4F. In the present study, the effects of amino acid substitutions in NK variants and G169A in DFE on their enzyme characteristics were evaluated. Pure proteins were obtained using two sequential steps chromatography using ion exchange and a gel filtration columns. Their activities were determined with fibrin plate, fibrin zymography, fibrinogen hydrolysis, and chromogenic assays. The fibrinogen degradation profile of the wild type NK (NatWT) was different to the NK variants but similar to DFEs. Optimum activity of all the NKs and DFEs was achieved at 50 °C while the optimum pH for NatWT/DFEs and NK variants were 8 and 7, respectively. DFE_G169A exhibited higher fibrinogen degradation rate and fibrin specific activity than DFE. PMSF inhibited all the NKs and DFEs while SDS and EDTA caused lower activity. The NK variants were more resistant towards Na⁺ and Ca²⁺ but more sensitive to K⁺. The amino acid substitutions in NK variants alter their fibrinogen degradation profile, optimum working pH, working pH range, and resistance to some ions. Substitutions in NK variants likely promote structural changes, particularly with the binding mode of the calcium ion cofactor. The results provide a beneficial basis for future development of fibrino(gen)olytic proteins with improved properties for cardiovascular diseases therapy.

Journal of Food Quality Evaluation of Effect of Extraction Solvent on Selected Properties of Olive Leaf Extract

The quest for natural preservatives and functional foods with health benefits has seen an increasing demand for natural products having therapeutic value. Herein, we investigated the influence of ethanol, methanol, acetone (50%, 70%, and 90% v/v), and distilled water on selected properties of olive leaf extract and determined the yield, total phenolic content (TPC), antioxidant activity, and antimicrobial activity. Extracts were analyzed for their oleuropein, hydroxytyrosol, and tyrosol contents by high-performance liquid chromatography (HPLC). The highest extraction yield of 20.41% was obtained when using 90 vol% methanol, while the highest total polyphenol contents of 232 and 231 mggallic-acid-equivalent/100 g were obtained for 90 vol% methanol and 90 vol% ethanol, respectively. Antioxidant activity was determined using the α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging assay, by determining the ferric reducing antioxidant power (FRAP), and using the Fe2+-chelating activity assay, which provided the highest values when 90 vol% methanol was used (33.84%, 0.75, and 12.91%, respectively). HPLC analysis showed that the highest oleuropein contents corresponded to the extracts obtained using 90 and 70 vol% methanol (26.10 ± 0.20 and 24.92 ± 1.22 g/L, respectively), and the highest antimicrobial activity was observed for 90 vol% methanol and distilled water. Olive leaf extracts using 90 vol% methanol had high levels of polyphenols and were highly antioxidant and antimicrobial. The results of this study facilitate the commercial applications of natural extracts with antioxidant and antibacterial activities and are expected to establish a foundation for further optimization studies.

Prospects of fibrinolytic proteases of bacteria from sea cucumber fermentation products as antithrombotic agent

Cardiovascular disease is among the largest contributors of premature mortality in the world caused by inflammation of blood vessels. The abnormalities provoke thrombus formation or thrombosis blocking blood vessels leading to strokes, heart attacks and coronary artery diseases. Increasing percentage of cardiovascular cases and deaths due to thrombosis has attracted researchers to look for newer thrombolysis agents. Commonly used drugs to treat thrombosis has been limited due to various side effects. Therefore, the search for sources of safer and cheaper fibrinolytic enzymes for handling thrombolysis continues. This study aimed to evaluate potentials of fibrinolytic protease of bacteria isolated from fermented seafood (sea cucumber) products as antithrombotic agents. Information was initially gathered from scientific publications identified using web-based tools including PubMed (National Center for Biotechnology Information), Science Direct (Scopus) and Web of Science (Thomson Reuters) using combinations of search terms including “fibrinolytic enzyme protease”, “endopeptidase”, “fermented food”, “sea cucumber”, “thrombolysis therapy,” “thrombolytic agent,” “fibrinolytic bacteria,” “fibrinolysis,” “protease producing bacteria,” “fibrin degradation,” “holothurians,” etc. We also searched for these terms in national and international organization technical reports and databases. This literature review reveals the prospects of fibrinolytic protease enzymes from bacteria from fermented seafood, particularly sea cucumber as novel antithrombotic agents.

Fermentation of Blackberry with L. plantarum JBMI F5 Enhance the Protection Effect on UVB-Mediated Photoaging in Human Foreskin Fibroblast and Hairless Mice through Regulation of MAPK/NF-κB Signaling

Chronic and extensive exposure of ultraviolet (UV)-irradiation causes human skin sunburn, inflammation, or photoaging, which is associated with downregulated collagen synthesis. This study investigated the effects of fermented blackberry (Rubus fruticosus B., FBB) by Lactobacillus plantarum JBMI F5 (LP) on UVB-induced photoaging in human foreskin fibroblast (Hs68) as well as in SKH-1 hairless mice. FBB pretreatment inhibited UVB-mediated type-1 procollagen degradation, matrix metalloproteinase (MMP)-1 and MMP-2 protein expression, and suppressed nuclear factor-κB (NF-κB) activation as well as mitogen-activated protein kinase (MAPK) phosphorylation in Hs68. In addition, FBB administration diminished the wrinkle formation in dorsal skin and epidermal thickening in UVB-irradiated hairless mice. Moreover, UVB-induced Type-1 procollagen reduction and antioxidant enzyme inactivation were reversed by FBB administration. These results suggest that FBB may have antiphotoaging effects on UVB-induced wrinkle formation by maintaining the extracellular matrix density in the dermis, which occurs via regulation of reactive oxygen species and related MAPK and NF-κB signaling. Therefore, FBB can be a potential candidate for protecting skin aging against UV irradiation.

Effects of Lotus (Nelumbo nucifera) Leaf on Quality and Antioxidant Activity of Yogurt during Refrigerated Storage

The supplementation with natural ingredients that are rich in polyphenols could improve the quality and functionality of yogurt. Lotus leaf (LL) are abundant in phenolic compounds. We aimed to investigate the effects of LL powder on the quality properties, total phenolic content (TPC), and antioxidant activity of yogurt. Yogurt was supplemented with four different concentrations (0%, 0.2%, 0.5%, and 1%) of LL powder and evaluated for 14 d refrigerated storage. During storage, the titratable acidity (TA) of all LL yogurt groups was higher than that of the control (p<0.05). The L* and a* values decreased by LL addition to the yogurts, while the b* values increased. All LL yogurt groups indicated better viscosity than that of control, and among them, 0.2% LL yogurts had the highest viscosity without significant decrease until the end of the storage duration. The addition of LL into yogurt enhanced the water-holding capacity (WHC) by at least 1.5-fold than that of control for the entire storage duration. The TPC of yogurts gradually increased with the addition of LL (p<0.05) and continued to increase during storage; the 1% LL yogurt at 14 d showed the highest value of 61.94±1.68 μg GAE/g. The DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity and reducing power of the yogurts were also significantly enhanced with increasing LL concentrations (p<0.05). These results suggest that lotus leaf may be useful as a natural ingredient for improving the quality and antioxidant activity of yogurt.

Purification and characterization of a novel, highly potent fibrinolytic enzyme from Bacillus subtilis DC27 screened from Douchi, a traditional Chinese fermented soybean food

The highly fibrinolytic enzyme-producing bacterium was identified as Bacillus subtilis DC27 and isolated from Douchi, a traditional fermented soybean food. The DFE27 enzyme was purified from the fermentation broth of B. subtilis DC27 by using UNOsphere Q column chromatography, Sephadex G-75 gel filtration, and high-performance liquid chromatography. It was 29 kDa in molecular mass and showed the optimal reaction temperature and pH value of 45 °C and 7.0, respectively, with a stable fibrinolytic activity below 50 °C and within the pH range of 6.0 to 10.0. DFE27 was identified as a serine protease due to its complete inhibition by phenylmethysulfony fluoride. The first 24 amino acid residues of the N-terminal sequence of the enzyme were AQSVPYGVSQIKAPALHSQGFTGS. The enzyme displayed the highest specificity toward the substrate D-Val-Leu-Lys-pNA for plasmin and it could not only directly degrade but also hydrolyze fibrin by activating plasminogen into plasmin. Overall, the DFE27 enzyme was obviously different from other known fibrinolytic enzymes in the optimum substrate specificity or fibrinolytic action mode, suggesting that it is a novel fibrinolytic enzyme and may have potential applications in the treatment and prevention of thrombosis.

Biochemical, Microbiological, and Sensory Characteristics of Stirred Yogurt Containing Red or Green Pepper (Capsicum annuum cv. Chungyang) Juice

Hot pepper has anti-obesity effects by controlling appetite and reducing blood fat level. To reduce the pungency of capsaicin, red or green hot pepper juice was fermented with Bacillus licheniformis SK1230. Fermented hot pepper juice was then added into yogurt at different ratios. The pH of yogurt added with hot pepper juice was decreased from 4.61 to 4.48. Titratable acidity and counts of lactic acid bacteria were increased with increasing amount of pepper juice added. However, the viscosity was decreased significantly compared to the control. On chromaticity test, when more pepper juice was added, L*-value was decreased whereas a*- and b*- values were increased significantly (p<0.05). The spectrum of antimicrobial activity of yogurt was slightly changed compared to using pepper juice. Total polyphenol contents and antioxidant activity were increased with increasing amount of pepper juice added. Stirred yogurt added with fermented red pepper juice at 3% or green pepper juice at 1% showed high scores in flavor, appearance, texture, and overall acceptance in sensory test. Yogurt added with fermented pepper juice with reduced pungency showed also good palatability during storage at 4°C. Yogurt with added hot pepper juice can be play an important role in functional food relative to anti-obesity.

Stepwise modifications of genetic parts reinforce the secretory production of nattokinase in Bacillus subtilis

Nattokinase (NK) is an important serine‐protease with direct fibrinolytic activity involving the prevention of cardiovascular disease as an antithrombotic agent. Dozens of studies have focused on the characterization of intrinsic novel promoters and signal peptides to the secretory production of recombinant proteins in Bacillus subtilis. However, intrinsic genetic elements have several drawbacks, which cannot mediate the production of NK to the desired level. In this study, the genetic elements, which were used to overproduce the recombinant secretory NK, were rationally modified in B. subtilis in a stepwise manner. The first step was to select a suitable signal peptide for the highly efficient secretion of NK. By comparison of the secretory levels mediated by two different signal peptides, which were encoded by the genes of a minor extracellular protease epr (SP_epr) and cell‐wall associated protease wapA (SP_wapA), respectively, SP_wapA was verified as the superior secretory element. Second, P04, which was a synthetic promoter screened from an array of mutants based on the promoter cloned from the operon of a quorum‐sensing associated gene srfA (P_srfA), was paired to SP_wapA. The secretory level of NK was obviously augmented by the combination of these two genetic elements. Third, the cis‐acting element CodY‐binding sequence positioned at the 5′UTR was deleted (yielding P08), and thus the secretory level was significantly elevated. The activity of NK, which was defined as fibrinolytic units (FU), reached to a level of 270 FU ml⁻¹. Finally, the superior genetic element composed of P08 and SP_wapA was utilized to overproduce NK in the host B. subtilis WB800, which was able to produce the secretory NK at 292 FU ml⁻¹. The strategy established in this study can not only be used to overproduce NK in B. subtilis but also might be a promising pipeline to modify the genetic element for the synthetic secretory system.

Evaluation of the Biogenic Amines Formation and Degradation Abilities of Lactobacillus curvatus From Chinese Bacon

Control of biogenic amines (BAs) is critical to guarantee the safety of fermented meat products. The aim of this study is to evaluate the BAs formation and degradation abilities of lactic acid bacteria from Chinese bacon to obtain the beneficial candidate for BAs control. Seven lactic acid bacteria were selected from the typical Chinese bacon products, identified as Lactobacillus curvatus by 16S rDNA analysis. Then, genes analysis and high-performance liquid chromatography (HPLC) analysis were performed to evaluate the BAs formation and degradation abilities of as-selected strains. All L. curvatus strains were confirmed to harbor the genes encoding the tyrosine decarboxylase and ornithine decarboxylase, and they could produce tyramine, β-phenethylamine, putrescine, and cadaverine. In comparison, the lowest concentration of total BAs was obtained in L. curvatus G-1. Meanwhile, all L. curvatus strains were positive in amines oxidase gene analysis, and they could also degrade six common BAs, especially the L. curvatus G-1 with the highest degradation percentage (above 40%) for each BA. Furthermore, fermented meat model analysis verified that the L. curvatus G-1 could significantly reduce BAs. In conclusion, L. curvatus G-1 shows a low BAs-producing ability, as well as a high BAs-degrading ability, and this study provides a promising candidate for potential BAs control in fermented meat products.

Antioxidant Activity and Quality Characteristics of Yogurt Added Green Olive Powder during Storage

The objective of this study was to determine the antioxidant and quality characteristics of yogurt added green olive powder stored at 4°С for 15 d. The following four groups were used in this study: Control group (GY0), Yogurt added with 1% green olive (GY1), with 3% green olive (GY3), and with 5% green olive (GY5). The more time of titratable acidity went by, the more it increased. Except GY0, viscosity tended to decrease in other groups (p>0.05), and the more time of syneresis went by, the more it increased, but GY3 of them showed the lowest syneresis. Lactic acid bacteria showed no significant with GY0 until 5 d, but after that, GY1, GY3 and GY5 showed lower than GY0. Yogurt added green olive showed darker color than GY0 (low L* and high a*). The antioxidant activity of GY5 was found to be the highest among the four groups at day 1 of storage. Total phenolic content, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, and reducing power of GY5 was found to be the highest among the four groups at day 1 of storage which were 6.96 mg GAE/kg, 47.53%, and 0.57, respectively. In the sensory evaluation sweet and overall of GY3 indicated the highest score among the four groups. Results of this study demonstrated that green olive powder might be used to improve the antioxidant capacity and sensory characteristics of yogurt.

Use of Bacillus amyloliquefaciens HZ-12 for High-Level Production of the Blood Glucose Lowering Compound, 1-Deoxynojirimycin (DNJ), and Nutraceutical Enriched Soybeans via Fermentation

1-Deoxynojirimycin (DNJ) is an efficient α-glucosidase inhibitor (α-GI) with potential applications in the prevention and treatment of diabetes. In this study, 16 Bacillus strains were screened for α-GI rate, and the strain HZ-12 with the highest α-GI rate was identified as Bacillus amyloliquefaciens through the analysis of physiological biochemical characteristics and 16S rDNA sequence. By LC-MS/Q-TOF analysis, the α-GI component produced by B. amyloliquefaciens HZ-12 was identified as DNJ. Soybean was used as the substrate for the solid-state fermentation; 870 mg/kg DNJ was produced by B. amyloliquefaciens HZ-12 after optimizing the fermentation conditions and media, which was 3.83-fold higher than the initial yield. Also, evaluations of nutraceutical enrichment in the form of anticoagulant activity, antioxidant activity, total nitrogen (TN), and total reducing sugars (TRS) of the B. amyloliquefaciens HZ-12 fermented soybeans were substantially higher than unfermented soybeans. This study provided a promising strain for high-level production of DNJ and produced nutraceutical enriched soybeans by fermentation.

Novel Sequential Screening and Enhanced Production of Fibrinolytic Enzyme by Bacillus sp. IND12 Using Response Surface Methodology in Solid-State Fermentation

Fibrinolytic enzymes have wide applications in clinical and waste treatment. Bacterial isolates were screened for fibrinolytic enzyme producing ability by skimmed milk agar plate using bromocresol green dye, fibrin plate method, zymography analysis, and goat blood clot lysis. After these sequential screenings, Bacillus sp. IND12 was selected for fibrinolytic enzyme production. Bacillus sp. IND12 effectively used cow dung for its growth and enzyme production (687 ± 6.5 U/g substrate). Further, the optimum bioprocess parameters were found out for maximum fibrinolytic enzyme production using cow dung as a low cost substrate under solid-state fermentation. Two-level full-factorial experiments revealed that moisture, pH, sucrose, peptone, and MgSO₄ were the vital parameters with statistical significance (p < 0.001). Three factors (moisture, sucrose, and MgSO₄) were further studied through experiments of central composite rotational design and response surface methodology. Enzyme production of optimized medium showed 4143 ± 12.31 U/g material, which was more than fourfold the initial enzyme production (978 ± 36.4 U/g). The analysis of variance showed that the developed response surface model was highly significant (p < 0.001). The fibrinolytic enzyme digested goat blood clot (100%), chicken skin (83 ± 3.6%), egg white (100%), and bovine serum albumin (29 ± 4.9%).

Expression of nattokinase in Escherichia coli and renaturation of its inclusion body

Nattokinase is an important fibrinolytic enzyme with therapeutic applications for cardiovascular diseases. The full-length and mature nattokinase genes were cloned from Bacillus subtilis var. natto and expressed in pQE30 vector in Escherichia coli. The full-length gene expressed low nattokinase activity in the intracellular soluble and the medium fractions. The mature gene expressed low soluble nattokinase activity and large amount insoluble protein in inclusion bodies without enzyme activity. Large amount of refolding solutions (RSs) at different pH values were screening and RS-10 and RS-11 at pH 9 were selected to refold nattokinase inclusion bodies. The recombinant cells were lysed with 0.1mg/mL lysozyme and ultrasonic treatment. After centrifugation, the pellete was washed twice with 20mM Tris-HCl buffer (pH 7.5) containing 1% Triton X-100 to purify the inclusion bodies. The inclusion bodies were dissolved in water at pH 12.0 and refolded with RS-10. The refolded proteins showed 42.8IU/mg and 79.3IU/mg fibrinolytic activity by the traditional dilution method (20-fold dilution into RS-10) and the directly mixing the protein solution with equal volume RS-10, respectively, compared to the 52.0IU/mg of total water-soluble proteins from B. subtilis var. natto. This work demonstrated that the inclusion body of recombinant nattokinase expressed in E. coli could be simply refolded to the natural enzyme activity level by directly mixing the protein solution with equal volume refolding solution.

Cow Dung Is a Novel Feedstock for Fibrinolytic Enzyme Production from Newly Isolated Bacillus sp. IND7 and Its Application in In Vitro Clot Lysis

Bacterial fibrinolytic enzymes find great applications to treat and prevent cardiovascular diseases. The novel fibrinolytic enzymes from food grade organisms are useful for thrombolytic therapy. This study reports fibrinolytic enzyme production by Bacillus sp. IND7 in solid-state fermentation (SSF). In this study, cow dung was used as the cheap substrate for the production of fibrinolytic enzyme. Enzyme production was primarily improved by optimizing the nutrient and physical factors by one-variable-at-a-time approach. A statistical method (two-level full factorial design) was applied to investigate the significant variables. Of the different variables, pH, starch, and beef extract significantly influenced on the production of fibrinolytic enzyme (p < 0.05). The optimum levels of these significant factors were further investigated using response surface methodology. The optimum conditions for enhanced fibrinolytic enzyme production were 1.23% (w/w) starch and 0.3% (w/w) beef extract with initial medium pH 9.0. Under the optimized conditions, cow dung substrate yielded 8,345 U/g substrate, and an overall 2.5-fold improvement in fibrinolytic enzyme production was achieved due to its optimization. This is the first report of fibrinolytic enzyme production using cow dung substrate from Bacillus sp. in SSF. The crude enzyme displayed potent activity on zymography and digested goat blood clot completely in in vitro condition.

A low cost fermentation medium for potential fibrinolytic enzyme production by a newly isolated marine bacterium, Shewanella sp. IND20

Agro-residues were used as the substrate for the production of fibrinolytic enzyme in solid state fermentation. In this study, two-level full factorial design (2⁵) and response surface methodology were applied to optimize a fermentation medium for the production of fibrinolytic enzyme from the marine isolate Shewanella sp. IND20. The 2⁵ factorial design demonstrated that the physical factors (pH and moisture) and nutrient factors (trehalose, casein, and sodium dihydrogen phosphate) had significant effect on fibrinolytic enzyme production. Central composite design was employed to search for the optimal concentration of the three factors, namely moisture, pH, and trehalose, and the experimental results were fitted with a second-order polynomial model at 99% level (p < 0.0001). The optimized medium showed 2751 U/mL of fibrinolytic activity, which was 2.5-fold higher than unoptimized medium. The molecular weight of fibrinolytic enzyme was found to be 55.5 kDa. The optimum pH and temperature were 8.0 and 50 °C, respectively.

Decreased tobacco-specific nitrosamines by microbial treatment with Bacillus amyloliquefaciens DA9 during the air-curing process of burley tobacco

Tobacco specific nitrosamines (TSNA) mainly consisting of N-nitrosonornicotine (NNN), N-nitrosoanatabine (NAT), N-nitrosoanabasine (NAB), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are a group of toxic components threatening human health. To inhibit TSNA formation in tobacco leaves, a high nitrite reductive strain with low nitrate reduction ability was isolated and applied to tobacco leaves in an attempt to lower the nitrite precursor of TSNA. By morphology, physiology, biochemistry, and 16S rDNA sequence analysis, the strain DA9 was identified as Bacillus amyloliquefaciens. Under the optimized fermentation parameters (glucose 40 g/L, NH4Cl 4 g/L, corn steep liquor 8 g/L, MnSO4 0.01 g/L, KH2PO4 1.0 g/L, MgSO4 0.3 g/L, initial pH 7.0, inoculum age 6 h, inoculum size 3%, temperature 37 °C), the maximum cell dentisity of 1.2 × 10(9) CFU/mL was obtained at 36 h. The DA9 cell suspensions were applied in the air-curing process of the Burley tobacco (Eyan 6) leaves. The treatment by DA9 cells lowered 32% of the nitrite content and 47% of total TSNA content in the tobacco leaves, and the concentrations of the NNN, NNK, and NAT were decreased by 48%, 12%, and 35%, respectively. Collectively, this study provides a promising strain and a novel strategy for decreasing TSNA during the air-curing process.

Efficient expression of nattokinase in Bacillus licheniformis: host strain construction and signal peptide optimization

Nattokinase (NK) possesses the potential for prevention and treatment of thrombus-related diseases. In this study, high-level expression of nattokinase was achieved in Bacillus licheniformis WX-02 via host strain construction and signal peptides optimization. First, ten genes (mpr, vpr, aprX, epr, bpr, wprA, aprE, bprA, hag, amyl) encoding for eight extracellular proteases, a flagellin and an amylase were deleted to obtain B. licheniformis BL10, which showed no extracellular proteases activity in gelatin zymography. Second, the gene fragments of P43 promoter, Svpr, nattokinase and TamyL were combined into pHY300PLK to form the expression vector pP43SNT. In BL10 (pP43SNT), the fermentation activity and product activity per unit of biomass of nattokinase reached 14.33 FU/mL and 2,187.71 FU/g respectively, which increased by 39 and 156 % compared to WX-02 (pP43SNT). Last, Svpr was replaced with SsacC and SbprA, and the maximum fermentation activity (33.83 FU/mL) was achieved using SsacC, which was 229 % higher than that of WX-02 (pP43SNT). The maximum NK fermentation activity in this study reaches the commercial production level of solid state fermentation, and this study provides a promising engineered strain for industrial production of nattokinase, as well as a potential platform host for expression of other target proteins.