Identification of a novel protease from the thermophilic Anoxybacillus kamchatkensis M1V and its application as laundry detergent additive

Purification, and characterization of detergent-compatible serine protease from Bacillussafensis strain PRN1: A sustainable alternative to hazardous chemicals in detergent industry

Owing to vast therapeutic, commercial, and industrial applications of microbial proteases microorganisms from different sources are being explored. In this regard, the gut microbiota of Monopteruscuchia were isolated and examined for the production of protease. All the isolates were primarily and secondarily screened on skim milk and gelatin agar plates. The protease-positive isolates were characterized morphologically, biochemically, and molecularly. Out of the 20 isolated strains,6 belonging to five different genera viz.Bacillus,Priestia,Aeromonas,Staphylococcus, and Serratia demonstrated proteolytic activity. Bacillussafensis strain PRN1 demonstrated the highest protease production and, thus, the largest hydrolytic clear zones in both skim milk agar (15 ± 1 mm) and gelatin (16 ± 1 mm) plates. The optimized parameters (time, pH, temperature, carbon, nitrogen) for highest protease activity and microbial growth of B.safensis strain PRN1 includes 72 h (OD600 = 0.56,1303 U/mL), pH 8 (OD600 = 0.83, 403.29 U/mL), 40 °C (OD600 = 1.75, 1849.11 U/mL), fructose (OD600 = 1.22, 1502 U/mL), and gelatin (OD600 = 1.88, 1015.33 U/mL). The enzyme was purified to homogeneity using salt-precipitation and gel filtration chromatography. The sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that the purified enzyme was a monomer of a molecular weight of ∼33 kDa. The protease demonstrated optimal activity at pH 8 and 60 °C. It was strongly inhibited by phenylmethylsulfonyl fluoride (PMSF), demonstrating that it belongs to the serine-proteases family. The compatibility of the enzyme with surfactants and commercial detergents demonstrates its potential use in the detergent industry. Furthermore, the purified enzyme showed antibacterial and blood-stain removal properties.

Biochemical characterization of immobilized recombinant subtilisin and synthesis and functional characterization of recombinant subtilisin capped silver and zinc oxide nanoparticles

This pioneering research explores the transformative potential of recombinant subtilisin, emphasizing its strategic immobilization and nanoparticle synthesis to elevate both stability and therapeutic efficacy. Achieving an impressive 95.25 % immobilization yield with 3 % alginate composed of sodium along with 0.2 M CaCl2 indicates heightened pH levels and thermal resistance, with optimal action around pH 10 as well as 80 °C temperature. Notably, the Ca-alginate-immobilized subtilisin exhibits exceptional storage longevity and recyclability, affirming its practical viability. Comprehensive analyses of the recombinant subtilisin under diverse conditions underscore its adaptability, reflected in kinetic enhancements with increased Vmax (10.7 ± 15 × 103 U/mg) and decreased Km (0.19 ± 0.3 mM) values post-immobilization using N-Suc-F-A-A-F-pNA. UV-visible spectroscopy confirms the successful capping of nanoparticles made of Ag and ZnO by recombinant subtilisin, imparting profound antibacterial efficacy against diverse organisms and compelling antioxidant properties. Cytotoxicity was detected against the MCF-7 breast cancer line of cells, exhibiting IC50 concentrations at 8.87 as well as 14.52 µg/mL of AgNP as well as ZnONP, correspondingly, indicating promising anticancer potential. Rigorous characterization, including FTIR, SEM-EDS, TGA and AFM robustly validate the properties of the capped nanoparticles. Beyond therapeutic implications, the investigation explores industrial applications, revealing the versatility of recombinant subtilisin in dehairing, blood clot dissolution, biosurfactant activity, and blood stain removal. In summary, this research unfolds the exceptional promise of recombinant subtilisin and its nanoparticles, presenting compelling opportunities for diverse therapeutic applications in medicine. These findings contribute substantively to biotechnology and healthcare and stimulate avenues for further innovation and exploration.

Molecular strategies to enhance the keratinase gene expression and its potential implications in poultry feed industry

The tons of keratin waste are produced by the poultry and meat industry which is an insoluble and protein-rich material found in hair, feathers, wool, and some epidermal wastes. These waste products could be degraded and recycled to recover protein, which can save our environment. One of the potential strategy to achieve this target is use of microbial biotreatment which is more convenient, cost-effective, and environment-friendly by formulating hydrolysate complexes that could be administered as protein supplements, bioactive peptides, or animal feed ingredients. Keratin degradation shows great promise for long-term protein and amino acid recycling. According to the MEROPS database, known keratinolytic enzymes currently belong to at least 14 different protease families, including S1, S8, S9, S10, S16, M3, M4, M14, M16, M28, M32, M36, M38, and M55. In addition to exogenous attack (proteases from families S9, S10, M14, M28, M38, and M55), the various keratinolytic enzymes also function via endo-attack (proteases from families S1, S8, S16, M4, M16, and M36). Biotechnological methods have shown great promise for enhancing keratinase expression in different strains of microbes and different protein engineering techniques in genetically modified microbes such as bacteria and some fungi to enhance keratinase production and activity. Some microbes produce specific keratinolytic enzymes that can effectively degrade keratin substrates. Keratinases have been successfully used in the leather, textile, and pharmaceutical industries. However, the production and efficiency of existing enzymes need to be optimized before they can be used more widely in other processes, such as the cost-effective pretreatment of chicken waste. These can be improved more effectively by using various biotechnological applications which could serve as the best and novel approach for recycling and degrading biomass. This paper provides practical insights about molecular strategies to enhance keratinase expression to effectively utilize various poultry wastes like feathers and feed ingredients like soybean pulp. Furthermore, it describes the future implications of engineered keratinases for environment friendly utilization of wastes and crop byproducts for their better use in the poultry feed industry.

Advances in recombinant protease production: current state and perspectives

Proteases, enzymes that catalyze the hydrolysis of peptide bonds in proteins, are important in the food industry, biotechnology, and medical fields. With increasing demand for proteases, there is a growing emphasis on enhancing their expression and production through microbial systems. However, proteases' native hosts often fall short in high-level expression and compatibility with downstream applications. As a result, the recombinant production of proteases has become a significant focus, offering a solution to these challenges. This review presents an overview of the current state of protease production in prokaryotic and eukaryotic expression systems, highlighting key findings and trends. In prokaryotic systems, the Bacillus spp. is the predominant host for proteinase expression. Yeasts are commonly used in eukaryotic systems. Recent advancements in protease engineering over the past five years, including rational design and directed evolution, are also highlighted. By exploring the progress in both expression systems and engineering techniques, this review provides a detailed understanding of the current landscape of recombinant protease research and its prospects for future advancements.

Gene expression and molecular characterization of recombinant subtilisin from Bacillus subtilis with antibacterial, antioxidant and anticancer properties

This study investigated the multifunctional attributes such as, antibacterial, antioxidant and anticancer potential of recombinant subtilisin. A codon-optimized subtilisin gene was synthesized from Bacillus subtilis and was successfully transformed into E. coli DH5α cells which was further induced for high level expression in E. coli BL21 (DE3). An affinity purified ~40 kDa recombinant subtilisin was obtained that revealed to be highly alkali-thermostable based on the thermodynamic parameters. The kinetic parameters were deduced that indicated higher affinity of N-Suc-F-A-A-F-pNA substrate towards subtilisin. Recombinant subtilisin demonstrated strong antibacterial activity against several pathogens and showed minimum inhibitory concentration of 0.06 μg/mL against B. licheniformis and also revealed high stability under the influence of several biochemical factors. It also displayed antioxidant potential in a dose dependent manner and exhibited cell cytotoxicity against A549 and MCF-7 cancerous cell lines with IC50 of 5 μM and 12 μM respectively. The identity of recombinant subtilisin was established by MALDI-TOF mass spectrum depicting desired mass peaks and N-terminal sequence as MRSK by MALDI-TOF-MS. The deduced N- terminal amino acid sequence by Edman degradation revealed high sequence similarity with subtilisins from Bacillus strains. The structural and functional analysis of recombinant antibacterial subtilisin was elucidated by Raman, circular dichroism and nuclear magnetic resonance spectroscopy and thermogravimetric analysis. The results contribute to the development of highly efficient subtilisin with enhanced catalytic properties making it a promising candidate for therapeutic applications in healthcare industries.

The genus Anoxybacillus: an emerging and versatile source of valuable biotechnological products

Thermophilic and alkaliphilic microorganisms are unique organisms that possess remarkable survival strategies, enabling them to thrive on a diverse range of substrates. Anoxybacillus, a genus of thermophilic and alkaliphilic bacteria, encompasses 24 species and 2 subspecies. In recent years, extensive research has unveiled the diverse array of thermostable enzymes within this relatively new genus, holding significant potential for industrial and environmental applications. The biomass of Anoxybacillus has demonstrated promising results in bioremediation techniques, while the recently discovered metabolites have exhibited potential in medicinal experiments. This review aims to provide an overview of the key experimental findings related to the biotechnological applications utilizing bacteria from the Anoxybacillus genus.

Anoxybacillus: an overview of a versatile genus with recent biotechnological applications

The Bacillaceae family members are considered to be a good source of microbial factories for biotechnological processes. In contrast to Bacillus and Geobacillus, Anoxybacillus, which would be thermophilic and spore-forming group of bacteria, is a relatively new genus firstly proposed in the year of 2000. The development of thermostable microbial enzymes, waste management and bioremediation processes would be a crucial parameter in the industrial sectors. There has been increasing interest in Anoxybacillus strains for biotechnological applications. Therefore, various Anoxybacillus strains isolated from different habitats have been explored and identified for biotechnological and industrial purposes such as enzyme production, bioremediation and biodegradation of toxic compounds. Certain strains have ability to produce exopolysaccharides possessing biological activities including antimicrobial, antioxidant and anticancer. This current review provides past and recent discoveries regarding Anoxybacillus strains and their potential biotechnological applications in enzyme industry, environmental processes and medicine.

Improving the catalytic activity of a detergent-compatible serine protease by rational design

Serine proteases are among the most important biological additives in various industries such as detergents, leather, animal feed and food. A serine protease gene, Fgapt4, from Fusarium graminearum 2697 was identified, cloned and expressed in Pichia pastoris. The optimal pH and temperature of FgAPT4 were 8.5 and 40°C, respectively. The relative activity was >30% even at 10°C. It had a wide range of pH stability (4.0-12.0) and detergent compatibility. To improve the catalytic activity, a strategy combining molecular docking and evolutionary analysis was adopted. Twelve amino acid residue sites and three loops (A, B and C) were selected as potential hot spots that might play critical roles in the enzyme's functional properties. Twenty-eight mutants targeting changes in individual sites or loops were designed, and mutations with good performance were combined. The best mutant was FgAPT4-M3 (Q70N/D142S/A143S/loop C). The specific activity and catalytic efficiency of FgAPT4-M3 increased by 1.6 (1008.5 vs. 385.9 U/mg) and 2.2-fold (3565.1 vs. 1106.3/s/mM), respectively. Computational analyses showed that the greater flexibility of the substrate pocket may be responsible for the increased catalytic activity. In addition, its application in detergents indicated that FgAPT4-M3 has great potential in washing.

Versatility of subtilisin: A review on structure, characteristics, and applications

Due to its thermostability and high pH compatibility, subtilisin is most known for its role as an additive for detergents in which it is categorized as a serine protease according to MEROPS database. Subtilisin is typically isolated from various bacterial species of the Bacillus genus such as Bacillus subtilis, B. amyloliquefaciens, B. licheniformis, and various other organisms. It is composed of 268-275 amino acid residues and is initially secreted in the precursor form, preprosubtilisin, which is composed of 29-residues signal peptide, 77-residues propeptide, and 275-residues active subtilisin. Subtilisin is known for the presence of high and low affinity calcium binding sites in its structure. Native subtilisin has general properties of thermostability, tolerance to neutral to high pH, broad specificity, and calcium-dependent stability, which contribute to the versatility of subtilisin applicability. Through protein engineering and immobilization technologies, many variants of subtilisin have been generated, which increase the applicability of subtilisin in various industries including detergent, food processing and packaging, synthesis of inhibitory peptides, therapeutic, and waste management applications.

Unconventional microbial proteases as promising tools for the production of bioactive protein hydrolysates

Enzymatic hydrolysis is the most prominent strategy to release bioactive peptides from different food proteins and protein-rich by-products. Unconventional microbial proteases (UMPs) have gaining increased attention for such purposes, particularly from the 2010s. In this review, we present and discuss aspects related to UMPs production, and their use to obtain bioactive protein hydrolysates. Antioxidant and anti-hypertensive potentials, commonly evaluated through in vitro testing, are mainly reported. The in vivo bioactivities of protein hydrolysates and peptides produced through UMPs action are highlighted. In addition to bioactivities, enzymatic hydrolysis acts by modulating the functional properties of proteins for potential food uses. The compiled literature indicates that UMPs are promising biocatalysts to generate bioactive protein hydrolysates, adding up to commercially available enzymes. From the recent interest on this topic, continuous and in-depth research is needed to advance toward the applicability and commercial utility of both UMPs and obtained hydrolysates.

Identification of industrial detergent enzymes by SDS-PAGE and MALDI-TOF mass spectrometry

An efficient method was proposed for routine analysis of the most widely used detergent enzymes.

Statistical optimization of thermostable alkaline protease from Bacillus cereus KM 05 using response surface methodology

OBJECTIVES

Proteases have gained great attention due to their enormous applications in food, tannery, detergent, photography and many other industries. Proteases rank third position in the production of enzymes. This paper targets to isolate a bacterium with high alkaline protease activity and optimization of its production conditions using Response Surface Methodology (RSM).

RESULTS

A bacterium isolated from soil contaminated with detergent exhibited clearance zone on skim milk agar medium with a protease activity of 22 U/ml. The bacterial strain was identified as Bacillus cereus KM05 and optimization of its production conditions were performed using statistical methods. Further optimization with Box Behnken design resulted in an increase in protease activity by 1.5-fold (28.6 U/ml). The protease enzyme was thermotolerant up to 70 °C with stability towards alkaline pH (pH 9). The enzyme was not affected by most of the metal ions and solvents. Moreover, the protease was also compatible with six commercial detergents tested. Densitometric analysis of the destained fabric materials following the detergent-enzyme treatment, revealed a stain removal efficiency of 97%.

CONCLUSION

The alkaline protease enzyme obtained was stable at different conditions with stain removal efficacy. Hence, the present alkaline protease could be used for detergent formulations.

Microbial alkaline serine proteases: Production, properties and applications

Proteolytic enzymes hold a pivotal position in numerous industrial processes where hydrolysis of protein molecules is required under precise conditions. The emerging trend of biotechnological applications in recent years has witnessed a renewed interest in alkaline serine proteases extending their utility in detergent, leather, textile, food and pharmaceutical industries. A variety of microorganisms have been reported to produce alkaline serine proteases on a large scale, however, extensive research to find an alkaline serine protease with desirable characteristics such as significant catalytic efficiency, expanded stability and broad substrate specificity is still ongoing. Although submerged fermentation dominates the commercial enzyme production, recent reports have emphasized on solid state fermentation technology which can reduce major cost associated with the enzyme production. In the present review, recent research on alkaline serine proteases along with their novel properties and production using solid state fermentation have been discussed.

Characterization and Diversity Analysis of the Extracellular Proteases of Thermophilic Anoxybacillus caldiproteolyticus 1A02591 From Deep-Sea Hydrothermal Vent Sediment

Protease-producing bacteria play key roles in the degradation of marine organic nitrogen. Although some deep-sea bacteria are found to produce proteases, there has been no report on protease-secreting Anoxybacillus from marine hydrothermal vent regions. Here, we analyzed the diversity and functions of the proteases, especially the extracellular proteases, of Anoxybacillus caldiproteolyticus 1A02591, a protease-secreting strain isolated from a deep-sea hydrothermal vent sediment of the East Pacific Ocean. Strain 1A02591 is a thermophilic bacterium with a strong protease-secreting ability, which displayed the maximum growth rate (0.139 h^–1) and extracellular protease production (307.99 U/mL) at 55°C. Strain 1A02591 contains 75 putative proteases, including 65 intracellular proteases and 10 extracellular proteases according to signal peptide prediction. When strain 1A02591 was cultured with casein, 12 proteases were identified in the secretome, in which metalloproteases (6/12) and serine proteases (4/12) accounted for the majority, and a thermolysin-like protease of the M4 family was the most abundant, suggesting that strain 1A02591 mainly secreted a thermophilic metalloprotease. Correspondingly, the secreted proteases of strain 1A02591 showed the highest activity at the temperature as high as 70°C, and was inhibited 70% by metalloprotease inhibitor o-phenanthroline and 50% by serine protease inhibitor phenylmethylsulfonyl fluoride. The secreted proteases could degrade different proteins, suggesting the role of strain 1A02591 in organic nitrogen degradation in deep-sea hydrothermal ecosystem. These results provide the first insight into the proteases of an Anoxybacillus strain from deep-sea hydrothermal ecosystem, which is helpful in understanding the function of Anoxybacillus in the marine biogeochemical cycle.

High level expression and biochemical characterization of an alkaline serine protease from Geobacillus stearothermophilus to prepare antihypertensive whey protein hydrolysate

BACKGROUND

Proteases are important for hydrolysis of proteins to generate peptides with many bioactivities. Thus, the development of novel proteases with high activities is meaningful to discover bioactive peptides. Because natural isolation from animal, plant and microbial sources is impractical to produce large quantities of proteases, gene cloning and expression of target protease are preferred.

RESULTS

In this study, an alkaline serine protease gene (GsProS8) from Geobacillus stearothermophilus was successfully cloned and expressed in Bacillus subtilis. The recombinant GsProS8 was produced with high protease activity of 3807 U/mL after high cell density fermentation. GsProS8 was then purified through ammonium sulfate precipitation and a two-step chromatographic method to obtain the homogeneous protease. The molecular mass of GsProS8 was estimated to be 27.2 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and 28.3 kDa by gel filtration. The optimal activity of GsProS8 was found to be pH 8.5 and 50 °C, respectively. The protease exhibited a broad substrate specificity and different kinetic parameters to casein and whey protein. Furthermore, the hydrolysis of whey protein using GsProS8 resulted in a large amount of peptides with high angiotensin-I-converting enzyme (ACE) inhibitory activity (IC₅₀ of 0.129 mg/mL).

CONCLUSIONS

GsProS8 could be a potential candidate for industrial applications, especially the preparation of antihypertensive peptides.

Heterologous expression and purification of keratinase from Actinomadura viridilutea DZ50: feather biodegradation and animal hide dehairing bioprocesses

The keratin-degrading bacterium Actinomadura viridilutea DZ50 secretes a keratinase (KERDZ) with potential industrial interest. Here, the kerDZ gene was extracellularly expressed in Escherichia coli BL21(DE3)pLysS using pTrc99A vector. The recombinant enzyme (rKERDZ) was purified and biochemically characterized. Results showed that the native and recombinant keratinases have similar biochemical characteristics. The conventional dehairing with lime and sodium sulfide degrades the hair to the extent that it cannot be recovered. Thus, these chemical processes become a major contributor to wastewater problem and create a lot of environmental concern. The complete dehairing was achieved with 2000 U/mL rKERDZ for 10 h at 40 °C. In fact, keratinase assisted dehairing entirely degraded chicken feather (45 mg) and removed wool/hair from rabbit, sheep, goat, or bovine' hides (1.6 kg) while preserving the collagen structure. The enzymatic process is the eco-friendly option that reduces biological (BOD) (50%) and chemical (COD) oxygen demands (60%) in leather processing. Consequently, the enzymatic hair removal process could solve the problem of post-treatments encountering the traditional leather processing. The enzymatic (rKERDZ) dehaired leather was analyzed by scanning electron microscopic (SEM) studies, which revealed similar fiber orientation and compactness compared with control sample. Those properties support that the rKERDZ enzyme-mediated process is greener to some extent than the traditional one.

Purification and Biochemical Characterization of a Novel Thermostable Serine Protease from Geobacillus sp. GS53

Proteases account for approximately 60% of the enzyme market in the world, and they are used in various industrial applications including the detergent industry. In this study, production and characterization of a novel serine protease of thermophilic Geobacillus sp. GS53 from Balçova geothermal region, İzmir, Turkey, were performed. The thermostable protease was purified through ammonium sulfate precipitation and anion-exchange chromatography. The results showed that the protease had 137.8 U mg^-1 of specific activity and optimally worked at 55 ^oC and pH 8. It was also active in a broad pH (4-10) and temperature (25-75 °C) ranges. The protease was highly stable at 85 °C and demonstrated relative stability at pH 4, 7, and 10. Also, the enzyme had high stability against organic solvents and surfactants; enzyme relative activity did not decrease below 81% upon preincubation for 10 min. Ca²⁺, Cu²⁺, and Zn²⁺ ions slightly induced protease activity. The protease was highly specific to casein, skim milk, Hammerstein casein, and BSA substrates. These results revealed that the protease might have a potential effect in a variety of industrial fields, especially the detergent industry, because of its high thermostability and stability to surfactants.

Extracellular Production, Characterization, and Engineering of a Polyextremotolerant Subtilisin-Like Protease From Feather-Degrading Thermoactinomyces vulgaris Strain CDF

Here, the gene encoding a subtilisin-like protease (protease Als) was cloned from Thermoactinomyces vulgaris strain CDF and expressed in Escherichia coli. The recombinant enzyme was released into the culture medium of E. coli as a mature form (mAls). Purified mAls displayed optimal activity at 60–70°C and pH 10.0 using azo-casein as the substrate, and showed a half-life of 13.8 h at 70°C. Moreover, the activity of thermostable mAls was comparable to or higher than those of mesophilic subtilisin Carlsberg and proteinase K at low temperatures (10–30°C). Protease Als was also stable in several organic solvents and showed high compatibility with commercial laundry detergents. Notably, mAls exhibited approximately 100% of its activity at 3 M NaCl, and showed enhanced thermostability with the increase of NaCl concentration up to 3 M. Protease Als possesses an excess of solvent-accessible acidic amino acid residues, which may account for the high halotolerance of the enzyme. Compared with homologous protease C2 from the same strain, protease Als exhibits substantially lower activity toward insoluble keratin substrates but efficiently hydrolyzes soluble keratin released from chicken feathers. Additionally, direct substitution of the substrate-binding site of protease Als with that of protease C2 improves its activity against insoluble keratin substrates. By virtue of its polyextremotolerant attribute and kerationolytic capacity, protease Als may find broad applications in various industries such as laundry detergents, food processing, non-aqueous biocatalysis, and feather processing.

Extremophile Microbial Communities and Enzymes for Bioenergetic Application Based on Multi-Omics Tools

Abstract: Genomic and proteomic advances in extremophile microorganism studies are increasingly demonstrating their ability to produce a variety of enzymes capable of converting biomass into bioenergy. Such microorganisms are found in environments with nutritional restrictions, anaerobic environments, high salinity, varying pH conditions and extreme natural environments such as hydrothermal vents, soda lakes, and Antarctic sediments. As extremophile microorganisms and their enzymes are found in widely disparate locations, they generate new possibilities and opportunities to explore biotechnological prospecting, including biofuels (biogas, hydrogen and ethanol) with an aim toward using multi-omics tools that shed light on biotechnological breakthroughs.

Revisiting the scope and applications of food enzymes from extremophiles

Microorganisms from extreme environments tend to undergo various adaptations due to environmental conditions such as extreme pH, temperature, salinity, heavy metals, and solvents. Thus, they produce enzymes with unique properties and high specificity, making them useful industrially, particularly in the food industries. Despite these enzymes' remarkable properties, only a few instances can be reported for actual exploitation in the food industry. This review's objectives are to highlight the properties of these enzymes and their prospects in the food industry. First, an introduction to extremophilic organisms is presented, followed by the categories and application of food enzymes from extremophiles. Then, the unique structural features of extremozymes are shown. This review also covers the prospective applications of extremozymes in the food industry in a broader sense, including degradation of toxins, deconstruction of polymers into monomers, and catalysis of multistep processes. Finally, the challenges in bioprocessing of extremozymes and applications in food are presented. PRACTICAL APPLICATIONS: Enzymes are important players in food processing and preservation. Extremozymes, by their nature, are ideal for a broad range of food processing applications, particularly those that require process conditions of extreme pH, temperature, and salinity. As the global food industry grows, so too will grow the need to research and develop food products that are diverse, safe, healthy, and nutritious. There is also the need to produce food in a sustainable way that generates less waste or maximizes waste valorization. We anticipate that extremozymes can meet some of the research and development needs of the food industry.

A biological clean processing approach for the valorization of speckled shrimp Metapenaeus monoceros by-product as a source of bioactive compounds

The efficiency of the proteolytic strain Anoxybacillus kamchatkensis M1V in the fermentation of speckled shrimp by-product was investigated for the recovery of a deproteinized bioactive hydrolysate. The biological activities of the resulting hydrolysate were also examined by applying several antioxidant and enzyme inhibitory assays. The strain M1V was found to produce high level of protease activity (2000 U/mL) when grown in media containing only shrimp powder at 25 g/L. The crude protease displayed a significant deproteinization capabiliy, with the best efficiency (48%) being recorded for an enzyme to substrate (E/S) ratio of 30 U/mg. Following the deproteinization, chitin was recovered and the authenticity was confirmed by Fourier-transform infrared spectroscopy (FTIR) analysis. On the other hand, the obtained hydrolysate showed a significant enzymatic inhibitory potential against acetylcholinesterase, tyrosinase, amylase, and angiotensin I convertase, and a strong antioxidant activity. Graphical Abstract.

Statistical Experimental Design Optimization of Microbial Proteases Production under Co-Culture Conditions for Chitin Recovery from Speckled Shrimp Metapenaeus monoceros By-Product

This study was designed with the aim to produce microbial proteases in presence of speckled shrimp by-product. For this reason, three strains belonging to Bacillus genus, namely, Aeribacillus pallidus VP3, Lysinibacillus fusiformis C250R, and Anoxybacillus kamchatkensis M1V were studied under co-culture procedure. A Taguchi L27 experimental design was applied to optimize the co-culture parameters. The experimental design was built with 9 factors (by-product powder concentration, the pH of the medium, the temperature, the sucrose concentration, the agitation speed, the inoculum sizes of VP3, M1V, and C250R strains, and the culture volume) at three different levels. The obtained results showed that a total protease activity of 8,182 U/mL could be achieved after 24 h of incubation in presence of 20 g/L shrimp by-product and 10 g/L sucrose, at an initial pH of 7, a 40°C temperature and absorbance, at 600 nm, of inoculum sizes of 0.1, 0.3, and 0.1 for VP3, M1V, and C250R strains, respectively. The agitation was set at 200 rpm, and the final volume was 25 mL. Taguchi's design allowed the identification of temperature, the inoculum size for strain VP3, the inoculum size for strain M1V, and the final culture volume as the most influencing variables. A Box-Behnken design with 27 experiments was carried out for the optimization of these four selected factors. Following such design, the highest protease production reached was 11,300 U/mL. This yield was obtained in a final culture volume of 15 mL containing 20 g/L shrimp by-product powder and 10 g/L sucrose and inoculated with VP3, C250R, and M1V strains at 0.05, 0.1, and 0.2, respectively. The flasks were incubated at 45°C for 24 h with shaking at 200 rpm. The efficiency of chitin extraction by co-cultivation was investigated under the latter conditions. The chitin yield from shells by-product was 16.7%. Fourier-Transform Infrared (FTIR) analysis of the obtained chitin displayed characteristic profiles similar to that of the commercial α-chitin.

Identification of a New Serine Alkaline Peptidase from the Moderately Halophilic Virgibacillus natechei sp. nov., Strain FarDT and its Application as Bioadditive for Peptide Synthesis and Laundry Detergent Formulations

A new peptidase designated as SAPV produced from a moderately halophilic Virgibacillus natechei sp. nov., strain FarD^T was investigated by purification to homogeneity followed by biochemical and molecular characterization purposes. Through optimization, it was determined that the optimum peptidase activity was 16,000 U/mL. It was achieved after 36 h incubation at 35°C in the optimized enzyme liquid medium (ELM) at pH 7.4 that contains only white shrimp shell by-product (60 g/L) as sole energy and carbon sources. The SAPV enzyme is a monomer protein with a molecular mass of 31 kDa as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and high-performance liquid chromatography (HPLC) gel filtration chromatography. The sequence of its NH₂-terminal amino-acid residues showed homology with those of Bacillus peptidases S8/S53 superfamily. The SAPV showed optimal activity at pH 9 and 60°C. Irreversible inhibition of enzyme activity by diiodopropyl fluorophosphates (DFP) and phenylmethanesulfonyl fluoride (PMSF) confirmed its belonging to the serine peptidases. Considering its interesting biochemical characterization, the sapV gene was cloned, sequenced, and heterologously overexpressed in the extracellular fraction of E. coli BL21(DE3)pLysS. The biochemical properties of the recombinant peptidase (rSAPV) were similar to those of the native one. The highest sequence identity value (97.66%) of SAPV was obtained with peptidase S8 from Virgibacillus massiliensis DSM 28587, with 9 amino-acid residues of difference. Interestingly, rSAPV showed an outstanding and high resistance to several organic solvents than SPVP from Aeribacillus pallidus VP3 and Thermolysin type X. Furthermore, rSAPV exhibited an excellent detergent stability and compatibility than Alcalase 2.4 L FG and Bioprotease N100L. Considering all these remarkable properties, rSAPV has attracted the interest of industrialists.