Optimization and scale-up of α-amylase production by Aspergillus oryzae using solid-state fermentation of edible oil cakes

Cell walls of filamentous fungi - challenges and opportunities for biotechnology

The cell wall of filamentous fungi is essential for growth and development, both of which are crucial for fermentations that play a vital role in the bioeconomy. It typically has an inner rigid core composed of chitin and beta-1,3-/beta-1,6-glucans and a rather gel-like outer layer containing other polysaccharides and glycoproteins varying between and within species. Only a fraction of filamentous fungal species is used for the biotechnological production of enzymes, organic acids, and bioactive compounds such as antibiotics in large amounts on a yearly basis by precision fermentation. Most of these products are secreted into the production medium and must therefore pass through fungal cell walls at high transfer rates. Thus, cell wall mutants have gained interest for industrial enzyme production, although the causal relationship between cell walls and productivity requires further elucidation. Additionally, the extraction of valuable biopolymers like chitin and chitosan from spent fungal biomass, which is predominantly composed of cell walls, represents an underexplored opportunity for circular bioeconomy. Questions persist regarding the effective extraction of these biopolymers from the cell wall and their repurposing in valorization processes. This review aims to address these issues and promote further research on understanding the cell walls in filamentous fungi to optimize their biotechnological use. KEY POINTS: • The highly complex cell walls of filamentous fungi are important for biotechnology. • Cell wall mutants show promising potential to improve industrial enzyme secretion. • Recent studies revealed enhanced avenues for chitin/chitosan from fungal biomass.

Optimization of thermostable amylolytic enzyme production from Bacillus cereus isolated from a recreational warm spring via Box Behnken design and response surface methodology

This study aimed to find a source for local amylase-producing microbes. Sixteen isolates were obtained from the water samples from the warm spring and characterized based on morphological and biochemical tests. The 16S rRNA molecular identification technique confirmed the most potent isolate as Bacillus cereus. The thermophilic property of the bacterium demonstrated that it could withstand temperatures of up to 80 °C. One-factor-at-a-time (OFAT) and Box Behnken Design (BBD) coupled with response surface methodology (RSM) optimization techniques were used to improve amylase production. OFAT established optimal physical parameter conditions as the starch concentration of 5% w/v, inoculum volume of 2% v/v, pH of 8, incubation temperature of 45 °C, and 48 h of incubation, leading to amylase activity of 172.6 U/mL by the isolated B. cereus. A quadratic mathematical model with a coefficient of determination (R2) of 0.9957 was established for the amylase production process. Enhanced amylase activity of 196.02 U/mL was achieved with BBD-RSM under optimal growth conditions of pH of 7, incubation time of 48 h, substrate concentration of 5% w/v of starch, and at 45 °C, a 1.2-fold increase compared to the OFAT method. The B. cereus strain isolated from the warm spring was a mildly thermophilic bacterium with the potential for synthesizing amylolytic enzymes with characteristics beneficial for commercial utilization.

Recent trends in production and potential applications of microbial amylases: A comprehensive review

α-amylases are vital biocatalysts that constitute a billion-dollar industry with a substantial and enduring global demand. Amylases hydrolyze the α-1,4-glycosidic linkages in starch polymers to generate maltose and malto-oligosaccharides subunits. Amylases are key enzymes that have promising applications in various industrial processes ranging from pharmaceutical, pulp and paper, textile food industries to bioremediation and biofuel sectors. Microbial enzymes have been widely used in industrial applications owing to their ease of availability, cost-effectiveness and better stability at extreme temperatures and pH. α-amylases derived from distinct microbial origins exhibit diverse characteristics, which make them suitable for specific applications. The routine application of immobilized enzymes has become a standard practice in the production of numerous industrial products across the pharmaceutical, chemical, and food industries. This review details the structural makeup of microbial α-amylase to understand its thermodynamic characteristics, aiming to identify key areas that could be targeted for improving the thermostability, pH tolerance and catalytic activity of α-amylase through various immobilization techniques or specific enzyme engineering methods. Additionally, the review briefly explores the enzyme production strategies, potential sources of α-amylases, and use of cost-effective and sustainable raw materials for enzyme production to obtain α-amylases with unconventional applications in various industrial sectors. Major hurdles, challenges and future prospects involving microbial α-amylases has been briefly discussed by considering its diverse applications in industrial bioprocessing.

Valorization of agro-industrial waste through solid-state fermentation: Mini review

Agriculture and industrial waste are produced in large volumes every year worldwide, causing serious concerns about their disposal. These wastes have high organic content, which microorganisms can easily assimilate into relevant value-added products. Valorization of agro-industrial waste is required for sustainable development. Solid state fermentation is an excellent method of utilizing waste for circular bioeconomy. Exploitation of agro-industrial waste as a substrate utilizing microorganisms for solid state fermentation provides beneficial products for use in industries and other fields. The use of waste reduces the cost of production of value-added products. This method is an environmentally friendly, economical and feasible approach for waste management. This review discusses the factors affecting the production of value-added products through solid state fermentation. It also discusses the valuable products from solid state fermentation technology, such as antibiotics, enzymes, organic acids, bioremediation, biosurfactants and biofertilizers. Challenges and future prospects are also presented.

Comparative evaluation of amylases in the oral phase of the INFOGEST static simulation of oro-gastric digestion

Amylases are crucial enzymes for dietary starch hydrolysis and essential to human digestive physiology. To simulate gastrointestinal (GI) digestion in vitro, amylases may be included in a short oral phase to mimic human salivary amylase (HSA) activity. Due to the high procurement cost of HSA, alternate porcine or microbial sources of amylases have been used. The major objective of this study was to evaluate the suitability of porcine pancreatic amylase (PPA) as an alternative to HSA in the INFOGEST 2.0 static simulation of oro-gastric digestion. To start, a comprehensive literature review was conducted to categorize oral phase methodologies. We determined that 14.1 % and 5.2 % of 262 studies used PPA and microbial amylases, respectively, in the oral phase. Amylolytic activity was confirmed by HPLC analysis of free maltose after simulated potato digestion. PPA and HSA exhibited comparable starch hydrolysis, while a fungal amylase showed significantly higher activity (P < 0.0001). To investigate suspected proteolytic "side activity" of PPA, pea protein digestion was simulated with HSA, PPA, or no amylase in the oral phase. Proteolytic activity was evaluated in gastric digestas by measurement of free amino nitrogen (FAN) by UV spectroscopy and free amino acids by HPLC. Relative peptide hydrolysis patterns were evaluated by SDS-PAGE and size exclusion chromatography (SEC). PPA treatment showed significantly higher proteolytic activity based on FAN and free amino acid analysis compared to HSA (Both P < 0.0001, one-way ANOVA), and qualitatively greater protein hydrolysis by SDS-PAGE and SEC analyses. These data unanimously confirm the unintended proteolytic activity of PPA in the oral phase that carries over to the gastric phase, potentially confounding analyses of protein digestibility and nutrient bioavailability. These findings suggest PPA should be avoided in the oral phase and confirm that HSA remains the preferred amylase for simulating human oral digestion.

Improving the Nutritional Profile of Intermediate Wheatgrass by Solid-State Fermentation with Aspergillus oryzae Strains

Aspergillus oryzae has been used to ferment various cereal grains throughout history, as seen in the examples of sake, soy sauce, and miso. It is known that this fermentation enhances the nutritional quality of the raw materials by breaking down complex molecules into simpler, more digestible forms and increasing the bioactive compounds. In this study, intermediate wheatgrass (IWG) was fermented with three different strains of A. oryzae suitable for making sake, soy sauce, and miso. Whole IWG flour was mixed with water (1:2 w/w), autoclaved at 121 °C for 20 min, cooled, mixed with A. oryzae spores, and fermented for seven days at 30 °C. Sugars, protein, amino acids, kojic acid, total phenolic content, total flavonoid content, and DPPH radical scavenging activity were measured. The protein content increased significantly (p < 0.05) from 18.0 g/100 g to over 30 g/100 g after seven days. Lysine showed a positive correlation with protein content across all three strains, with its ratio increasing as the protein content increased, while all other essential amino acids displayed a negative correlation and a decreasing ratio with the protein content. Autoclaving increased the verbascose content of IWG, and further increases were observed during the first two days of fermentation across all three strains, followed by a subsequent decline. Peak glucose content was observed on days 3~4 but also decreased in the subsequent days. Total phenolic content, total flavonoid content, kojic acid, and DPPH scavenging activity peaked around day 4~5 for all three strains, followed by a slight decrease in the subsequent days. The findings of this study highlight the potential of solid-state fermentation to improve the nutritional profile of IWG, emphasizing that the selection of A. oryzae strains and the fermentation duration can affect the fermentation outcome and nutritional enhancements.

Saccharification and co-fermentation of lignocellulosic biomass by a cockroach-gut bacterial symbiont and yeast cocktail for bioethanol production

BACKGROUND

The eco-friendly transformation of agro-industrial wastes through microbial bioconversion could address sustainability challenges in line with the United Nations' Sustainable Development Goals. The bulk of agro-industrial waste consists of lignocellulosic materials with fermentable sugars, predominantly cellulose and hemicellulose. A number of pretreatment options have been employed for material saccharification toward successful fermentation into second-generation bioethanol. Biological and/or enzymatic pretreatment of lignocellulosic waste substrates offers eco-friendly and sustainable second-generation bioethanol production opportunities that may also contribute to waste management without affecting food security. In this study, we isolated a promising filamentous bacterium from the guts of cockroaches with commendable cellulolytic activity. The matrices of sequential statistics, from one-factor-at-a-time (OFAT) through significant variable screening by Placket-Burman design (PBD) to Box‒Behnken design of a surface methodology (BBD-RSM), were employed for major medium variable modeling and optimization by solid-state fermentation. The optimized solutions were used to saccharify lignocellulose in real time, and the kinetics of reducing sugar accumulation were subsequently evaluated to determine the maximum concentration of sugars extracted from the lignocellulose. The hydrolysate with the highest reducing sugar concentration was subjected to fermentation by Saccharomyces cerevisiae, Klyuveromyces marxianus and a mixture of both, after which the ethanol yield, concentration and fermentation efficiency were determined.

RESULTS

Sequential statistics revealed that rice husk powder, corn cob powder, peptone and inoculum volume were significant variables for the bioprocess at 59.8% (w/w) rice husk powder, 17.8% (w/w) corn cob powder, 38.8% (v/w; 109 cfu/mL) inoculum volume, and 5.3% (w/w) peptone. These conditions mediated maximum cellulolytic and xylanolytic activities of 219.93 ± 18.64 FPU/mL and 333.44 ± 22.74 U/mL, respectively. The kinetics of saccharification of the lignocellulosic waste under optimized conditions revealed two peaks of reducing sugar accumulation between 16 and 32 h and another between 56 and 64 h.

CONCLUSIONS

Although K. marxianus had a significantly greater fermentation efficiency than S. cerevisiae, fermentation with a 50:50 (% v/v) mixture of both yeasts led to 88.32% fermentation efficiency with 55.56 ± 0.19 g/L crude bioethanol, suggesting that inexpensive, eco-friendly and sustainable bioethanol production could be obtained from renewable energy sources.

Characterization of a novel subfamily 1.4 lipase from Bacillus licheniformis IBRL-CHS2: Cloning and expression optimization

This study focuses on a novel lipase from Bacillus licheniformis IBRL-CHS2. The lipase gene was cloned into the pGEM-T Easy vector, and its sequences were registered in GenBank (KU984433 and AOT80658). It was identified as a member of the bacterial lipase subfamily 1.4. The pCold I vector and E. coli BL21 (DE3) host were utilized for expression, with the best results obtained by removing the enzyme's signal peptide. Optimal conditions were found to be 15°C for 24 h, using 0.2 mM Isopropyl β-D-1-thiogalactopyranoside (IPTG). The His-tagged lipase was purified 13-fold with a 68% recovery and a specific activity of 331.3 U/mg using affinity purification. The lipase demonstrated optimal activity at 35°C and pH 7. It remained stable after 24 h in 25% (v/v) organic solvents such as isooctane, n-hexane, dimethyl sulfoxide (DMSO), and methanol, which enhanced its activity. Chloroform and diethyl ether inhibited the lipase. The enzyme exhibited the highest affinity for p-nitrophenol laurate (C12:0) with a Km of 0.36 mM and a Vmax of 357 μmol min-1 mg-1. Among natural oils, it performed best with coconut oil and worst with olive oil. The lipase was stable in the presence of 1 mM and 5 mM Ca2⁺, K⁺, Na⁺, Mg2⁺, and Ba2⁺, but its activity decreased with Zn2⁺ and Al3⁺. Non-ionic surfactants like Triton X-100, Nonidet P40, Tween 20, and Tween 40 boosted activity, while Sodium Dodecyl Sulfate (SDS) inhibited it. This lipase's unique properties, particularly its stability in organic solvents, make it suitable for applications in organic synthesis and various industries.

Optimization and purification of a novel calcium-independent thermostable, α-amylase produced by Bacillus licheniformis UDS-5

Microbial amylases should essentially remain active at higher temperatures, and in the alkaline pH and a range of surfactants to be suitable as detergent additives. In the present study, a thermophilic amylase producing bacterium, Bacillus licheniformis UDS-5 was isolated from Unai hot water spring in Gujarat, India. It was identified as a potent amylase producer during starch plate-based screening process. Therefore, the physicochemical parameters influencing amylase production were optimized using Plackett-Burman design and Central Composite Design. The amylase was purified through ammonium sulfate precipitation, size exclusion and ion exchange chromatography, achieving the purification fold and yield to be 9.2 and 40.6%, respectively. The enzyme displayed robust stability and activity across a wide range of temperatures and pHs, with an increased half-life and reduced deactivation rate constant. The amylase exhibited optimal catalysis at 70 °C and pH 8. The kinetic studies revealed Km and Vmax values of 0.58 mg/mL and 2528 μmol/mL/min, respectively. Besides, the purified amylase displayed stability in the presence of various metal ions, surfactants, and chelators suggesting its potential for industrial applications, particularly in the detergent industry. Moreover, detergent application studies demonstrated its efficacy in enhancing washing performance. A comparative profile on washing efficiency of the studied amylase and the commercial amylase with various detergents pointed towards its possible future use as a detergent additive.

Production and characterization of protease enzyme from Acinetobacter pittii using peanut meal as substrate

A significantly high protease enzyme yield of 617 U/ml was achieved with Acinetobacter pittii as the microorganism and peanut oil meal as the substrate. Peanut oil meal, which consists of proteins (40-60%) and carbohydrates (22-30%), serves as a sufficient source of nitrogen and carbon necessary for microbial growth and production of enzymes. Moreover, peanut meal offers the advantages of being affordable and available in large quantities, making the meal suitable for cost-effective enzyme production. In the present study, two bacterial strains and one fungal strain were selected to produce proteases utilizing peanut oil meal as the substrate. The experimental conditions during the enzyme production, including pH and temperature, were optimized. In addition, the substrate was enriched with various carbon and nitrogen sources. The microbial strains were streaked on nutritional agar (for bacteria) and potato dextrose agar (for fungus). Following an incubation period, the plates were stored at 4°C for further studies. The molecular weight of partially purified proteases of Acinetobacter pittii was found to be ≅ 95.5 kDa. Potassium nitrate was the most ideal nitrogen source (up to 411% increase in activity) and fructose was the best carbon source (425% increase). These enzymes exhibited excellent temperature tolerance and were capable of functioning over a wide pH range. Furthermore, the obtained proteases demonstrated ability to coagulate milk effectively, indicating their potential for various food-related applications.

The importance of acetate, pyruvate, and citrate feeding times in improving xanthan production by Xanthomonas citri

Xanthan gum is a microbial polysaccharide produced by Xanthomonas and widely used in various industries. To produce xanthan gum, the native Xanthomonas citri-386 was used in a cheese-whey-based culture medium. The culture conditions were investigated in batch experiments based on the response surface methodology to increase xanthan production and viscosity. Three independent variables in this study included feeding times of acetate, pyruvate, and citrate. The maximum xanthan gum production and viscosity within 120 h by X. citri-386 using Box-Behnken design were 25.7 g/l and 65 500 cP, respectively, with a 151% and 394% increase as compared to the control sample. Overall, the findings of this study recommend the use of X. citri-386 in the cheese-whey-based medium as an economical medium with optimal amounts of acetate, pyruvate, and citrate for commercial production of xanthan gum on an industrial scale. The adjustment of the pyruvate and acetate concentrations optimized xanthan gum production in the environment.

Enhanced saccharification levels of corn starch using as a strategy a novel amylolytic complex (AmyHb) from the thermophilic fungus Humicola brevis var. thermoidea in association with commercial enzyme

Amylases represent a versatile group of catalysts that are used for the saccharification of starch because they can hydrolyze the glycosidic bonds of starch molecules to release glucose, maltose, and short-chain oligosaccharides. The amylolytic complex of the thermophilic filamentous fungus Humicola brevis var. thermoidea (AmyHb) was produced, biochemically characterized, and compared with the commercial amylase Termamyl. In addition, the biotechnological application of AmyHb in starch saccharification was investigated. The highest production was achieved using a wheat bran medium at 50 °C for 5-6 days in solid-state fermentation (849.6 ± 18.2 U·g-1) without the addition of inducers. Optimum amylolytic activity occurred at pH 5.0 at 60 °C, and stability was maintained between pH 5.0 and 6.0, with thermal stability at 50-60 °C, especially in the presence of Ca2+. These results were superior to those found with Termamyl. Both enzymes were strongly inhibited by Hg2+, Cu2+, and Ag+; however, AmyHb displayed increased activity in the presence of Mn2+ and Na+. In addition, AmyHb showed greater tolerance to a wide range of ethanol concentrations. AmyHb appears to be a complex consisting of glucoamylase and α-amylase, based on its substrate specificity and TLC. The hydrolysis tests on cornstarch flour showed that the cocktail of AmyHb50% + Termamyl50% significantly increased the release of glucose and total reducing sugars (36.6%) when compared to the enzymes alone. AmyHb exhibited promising physicochemical properties and good performance with commercial amylase; therefore, this complex is a biotechnological alternative candidate for the bioprocessing of starch sources.

Purification and biochemical characterization of novel α-amylase and cellulase from Bacillus sp. PM06

Bacillus sp. PM06, previously isolated from sugarcane waste pressmud, could produce dual enzymes α-amylase and cellulase. The isolate's crude enzymes were purified homogeneously using ammonium sulfate precipitation followed by High Quaternary amine anion exchange chromatography. Purified enzymes revealed the molecular weights of α-amylase and cellulase as 55 and 52 kDa, with a purification fold of 15.4 and 11.5, respectively. The specific activity of purified α-amylase and cellulase were 740.7 and 555.6 U/mg, respectively. It demonstrated a wide range of activity from pH 5.0 to 8.5, with an optimum pH of 5.5 and 6.4 for α-amylase and cellulase. The optimum temperature was 50 °C for α-amylase and 60 °C for cellulase. The kinetic parameters of purified α-amylase were 741.5 ± 3.75 µmol/min/mg, 1.154 ± 0.1 mM, and 589 ± 3.5/(s mM), using starch as a substrate. Whereas cellulase showed 556.3 ± 1.3 µmol/min/mg, 1.78 ± 0.1 mM, and 270.9 ± 3.8/(s mM) of Vmax, Km, Kcat/Km, respectively, using carboxymethyl cellulose (CMC) as substrate. Among the various substrates tested, α-amylase had a higher specificity for amylose and CMC for cellulase. Different inhibitors and activators were also examined. Ca2+ Mg2+, Co2+, and Mn2+ boosted α-amylase and cellulase activities. Cu2+ and Ni2+ both inhibited the enzyme activities. Enzymatic saccharification of wheat bran yielded 253.61 ± 1.7 and 147.5 ± 1.0 mg/g of reducing sugar within 12 and 24 h of incubation when treated with purified α-amylase and cellulase. A more significant amount of 397.7 ± 1.9 mg/g reducing sugars was released from wheat bran due to the synergetic effect of two enzymes. According to scanning electron micrograph analysis, wheat bran was effectively broken down by both enzymes.

Characteristics and kinetics of thermophilic actinomycetes' amylase production on agro-wastes and its application for ethanol fermentation

Thermophilic actinomycetes are commonly found in extreme environments and can thrive and adapt to extreme conditions. These organisms exhibit substantial variation and garnered significant interest due to their remarkable enzymatic activities. This study evaluated the potential of Streptomyces griseorubens NBR14 and Nocardiopsis synnemataformans NBRM9 strains to produce thermo-stable amylase via submerged fermentation using wheat and bean straw. The Box-Behnken design was utilized to determine the optimum parameters for amylase biosynthesis. Subsequently, amylase underwent partial purification and characterization. Furthermore, the obtained hydrolysate was applied for ethanol fermentation using Saccharomyces cerevisiae. The optimal parameters for obtaining the highest amylase activity by NBR14 (7.72 U/mL) and NBRM9 (26.54 U/mL) strains were found to be 40 and 30 °C, pH values of 7, incubation time of 7 days, and substrate concentration (3 and 2 g/100 mL), respectively. The NBR14 and NBRM9 amylase were partially purified, resulting in specific activities of 251.15 and 144.84 U/mg, as well as purification factors of 3.91 and 2.69-fold, respectively. After partial purification, the amylase extracted from NBR14 and NBRM9 showed the highest activity level at pH values of 9 and 7 and temperatures of 50 and 60 °C, respectively. The findings also indicated that the maximum velocity (Vmax) for NBR14 and NBRM9 amylase were 57.80 and 59.88 U/mL, respectively, with Km constants of 1.39 and 1.479 mM. After 48 h, bioethanol was produced at concentrations of 5.95 mg/mL and 9.29 mg/mL from hydrolyzed wheat and bean straw, respectively, through fermentation with S. cerevisiae. Thermophilic actinomycetes and their α-amylase yield demonstrated promising potential for sustainable bio-ethanol production from agro-byproducts.

Amylase and Cellulase Production from Newly Isolated Bacillus subtilis Using Acid Treated Potato Peel Waste

Species belonging to the genus Bacillus produce many advantageous extracellular enzymes that have tremendous applications on a commercial scale for the textile, detergent, feed, food, and beverage industries. This study aimed to isolate potent thermo-tolerant amylolytic and cellulolytic bacterium from the local environment. Using the Box-Behnken design of response surface methodology, we further optimized the amylase and cellulase activity. The isolate was identified by 16S rRNA gene sequencing as Bacillus subtilis QY4. This study utilized potato peel waste (PPW) as the biomaterial, which is excessively being dumped in an open environment. Nutritional status of the dried PPW was determined by proximate analysis. All experimental runs were carried out in 250 mL Erlenmeyer flasks containing acid treated PPW as a substrate by the thermos-tolerant Bacillus subtilis QY4 incubated at 37 °C for 72 h of submerged fermentation. Results revealed that the dilute H2SO4 assisted autoclaved treatment favored more amylase production (0.601 IU/mL/min) compared to the acid treatment whereas high cellulase production (1.269 IU/mL/min) was observed in the dilute acid treatment and was found to be very effective compared to the acid assisted autoclaved treatment. The p-value, F-value, and coefficient of determination proved the significance of the model. These results suggest that PPW could be sustainably used to produce enzymes, which offer tremendous applications in various industrial arrays, particularly in biofuel production.

Aspergillus oryzae as a Cell Factory: Research and Applications in Industrial Production

Aspergillus oryzae, a biosafe strain widely utilized in bioproduction and fermentation technology, exhibits a robust hydrolytic enzyme secretion system. Therefore, it is frequently employed as a cell factory for industrial enzyme production. Moreover, A. oryzae has the ability to synthesize various secondary metabolites, such as kojic acid and L-malic acid. Nevertheless, the complex secretion system and protein expression regulation mechanism of A. oryzae pose challenges for expressing numerous heterologous products. By leveraging synthetic biology and novel genetic engineering techniques, A. oryzae has emerged as an ideal candidate for constructing cell factories. In this review, we provide an overview of the latest advancements in the application of A. oryzae-based cell factories in industrial production. These studies suggest that metabolic engineering and optimization of protein expression regulation are key elements in realizing the widespread industrial application of A. oryzae cell factories. It is anticipated that this review will pave the way for more effective approaches and research avenues in the future implementation of A. oryzae cell factories in industrial production.

Komagataella phaffii as a Platform for Heterologous Expression of Enzymes Used for Industry

In the 1980s, Escherichia coli was the preferred host for heterologous protein expression owing to its capacity for rapid growth in complex media; well-studied genetics; rapid and direct transformation with foreign DNA; and easily scalable fermentation. Despite the relative ease of use of E. coli for achieving the high expression of many recombinant proteins, for some proteins, e.g., membrane proteins or proteins of eukaryotic origin, this approach can be rather ineffective. Another microorganism long-used and popular as an expression system is baker's yeast, Saccharomyces cerevisiae. In spite of a number of obvious advantages of these yeasts as host cells, there are some limitations on their use as expression systems, for example, inefficient secretion, misfolding, hyperglycosylation, and aberrant proteolytic processing of proteins. Over the past decade, nontraditional yeast species have been adapted to the role of alternative hosts for the production of recombinant proteins, e.g., Komagataella phaffii, Yarrowia lipolytica, and Schizosaccharomyces pombe. These yeast species' several physiological characteristics (that are different from those of S. cerevisiae), such as faster growth on cheap carbon sources and higher secretion capacity, make them practical alternative hosts for biotechnological purposes. Currently, the K. phaffii-based expression system is one of the most popular for the production of heterologous proteins. Along with the low secretion of endogenous proteins, K. phaffii efficiently produces and secretes heterologous proteins in high yields, thereby reducing the cost of purifying the latter. This review will discuss practical approaches and technological solutions for the efficient expression of recombinant proteins in K. phaffii, mainly based on the example of enzymes used for the feed industry.

Extracellular enzymes producing yeasts study: cost-effective production of α-amylase by a newly isolated thermophilic yeast Geotrichum candidum PO27

Enzymes are biocatalysts mainly used for their industrial potential in various applications. The present study aims to understand the enzyme production for biotechnological interest from a local yeast strain. From 100 isolates obtained from various biotopes, 78 strains were selected for their enzymatic heritage. Screening of α-amylase, lipase/esterase, and cellulase activities by rapid plate detection methods was carried out and the PO27 yeast was selected for its high capacity to produce α-amylase. In addition, this yeast strain exhibited good lipolytic and esterolytic activities, as well as low cellulase activity. A sequence analysis of the D1/D2 region of the 26S ribosomal RNA (26S rRNA) and a study of morphological characteristics identified the PO27 strain as Geotrichum candidum. The production of α-amylase has been studied in solid medium fermentation using various natural substrates without any supplementation such as olive pomace, potato peels, leftover bread, and mastic cake. G. candidum PO27 showed an improved production of α-amylase with olive pomace, thus reaching approximately 180.71 U/g. To evaluate the ability of this isolate to produce α-amylase in submerged fermentation, multiple concentrations of olive pomace substrate were tested. The best activity of submerged fermentation was statistically compared to the solid-state fermentation result in order to select the appropriate fermentation type. A high significant difference was found to rank the 6% olive pomace medium as the best substrate concentration with 34.395 U/mL of α-amylase activity. This work showed that the new isolate Geotrichum candidum PO27 has a better potential to produce α-amylase at a low cost in solid-state fermentation compared to submerged fermentation. Optimization conditions for PO27 α-amylase production through solid-state fermentation were achieved ‎ using a one factor at a time (OFAT) approach. The findings revealed that a high temperature (60 °C), an acidic pH, malt extract, and soluble starch were the highly significant medium components for enhancing α-‎amylase production. The use of olive pomace waste by Geotrichum candidum PO27 is expected to be effective in producing an industrially useful α-amylase.

Biochemical characterization of an acid-thermostable glucoamylase from Aspergillus japonicus with potential application in the paper bio-deinking

Aspergillus species have been highlighted in enzyme production looking for industrial applications, notably, amylases are one of the most interesting enzymes. They are capable of hydrolyzing α-glycosidic linkages of starch and widely used in industrial processes to produce ethanol, glucose, and fructose syrup as well as in the textiles, detergents, and paper industries applications. In this context, this work aimed at the biochemical characterization of the glucoamylase from Aspergillus japonicus and its application in the bio-bleaching process of recycled paper. The optimum temperature and pH for the glucoamylase assay were standardized as 50°C and 5.5. After 1 h of incubation, glucoamylase retained 90% of its activity at 30-50°C. It also kept 70% of its activity in the pH range of 4.0-6.5 after an hour of incubation. The enzyme led to an increase of 30% in the relative whiteness of 10 dry grams of sulfite paper and magazine paper when applied along with commercial cellulase and 10 mM MnCl2 . In addition, after the treatments, the glucoamylase recovered activity was 30%-32%, which indicates a prolonged availability of the enzyme and can considerably curtail the redundant downstream process of the recycled paper bio-bleaching. Thus, the glucoamylase from A. japonicus has a significant role in bio-bleaching recycled paper, reducing the necessity of hard chemicals, and improving the industrial process in an interesting economic and ecological mode.

Challenges and prospects of microbial α-amylases for industrial application: a review

α-Amylases are essential biocatalysts representing a billion-dollar market with significant long-term global demand. They have varied applications ranging from detergent, textile, and food sectors such as bakery to, more recently, biofuel industries. Microbial α-amylases have distinct advantages over their plant and animal counterparts owing to generally good activities and better stability at temperature and pH extremes. With the scope of applications expanding, the need for new and improved α-amylases is ever-growing. However, scaling up microbial α-amylase technology from the laboratory to industry for practical applications is impeded by several issues, ranging from mass transfer limitations, low enzyme yields, and energy-intensive product recovery that adds to high production costs. This review highlights the major challenges and prospects for the production of microbial α-amylases, considering the various avenues of industrial bioprocessing such as culture-independent approaches, nutrient optimization, bioreactor operations with design improvements, and product down-streaming approaches towards developing efficient α-amylases with high activity and recyclability. Since the sequence and structure of the enzyme play a crucial role in modulating its functional properties, we have also tried to analyze the structural composition of microbial α-amylase as a guide to its thermodynamic properties to identify the areas that can be targeted for enhancing the catalytic activity and thermostability of the enzyme through varied immobilization or selective enzyme engineering approaches. Also, the utilization of inexpensive and renewable substrates for enzyme production to isolate α-amylases with non-conventional applications has been briefly discussed.

Characterization of an α-Amylase from the Honeybee Chalk Brood Pathogen Ascosphaera apis

The insect pathogenic fungus, Ascosphaera apis, is the causative agent of honeybee chalk brood disease. Amylases are secreted by many plant pathogenic fungi to access host nutrients through the metabolism of starch, and the identification of new amylases can have important biotechnological applications. Production of amylase by A. apis in submerged culture was optimized using the response surface method (RSM). Media composition was modeled using Box-Behnken design (BBD) at three levels of three variables, and the model was experimentally validated to predict amylase activity (R2 = 0.9528). Amylase activity was highest (45.28 ± 1.16 U/mL, mean ± SE) in media composed of 46 g/L maltose and1.51 g/L CaCl2 at a pH of 6.6, where total activity was ~11-fold greater as compared to standard basal media. The enzyme was purified to homogeneity with a 2.5% yield and 14-fold purification. The purified enzyme had a molecular weight of 75 kDa and was thermostable and active in a broad pH range (> 80% activity at a pH range of 7-10), with optimal activity at 55 °C and pH = 7.5. Kinetic analyses revealed a Km of 6.22 mmol/L and a Vmax of 4.21 μmol/mL·min using soluble starch as the substrate. Activity was significantly stimulated by Fe2+ and completely inhibited by Cu2+, Mn2+, and Ba2+ (10 mM). Ethanol and chloroform (10% v/v) also caused significant levels of inhibition. The purified amylase essentially exhibited activity only on hydrolyzed soluble starch, producing mainly glucose and maltose, indicating that it is an endo-amylase (α-amylase). Amylase activity peaked at 99.38 U/mL fermented in a 3.7 L-bioreactor (2.15-fold greater than what was observed in flask cultures). These data provide a strategy for optimizing the production of enzymes from fungi and provide insight into the α-amylase of A. apis.

Effects of fermented feed on growth performance, serum biochemical indexes, antioxidant capacity, and intestinal health of lion-head goslings

Introduction

The aim of this study was to evaluate the effects of fermented feed on growth performance, antioxidant indexes and intestinal health in lion-head goslings.

Methods

288 male lion-head goslings (one-day-old) were randomly divided into four groups (6 replicates per group, 12 samples per replicate): control group (basal diet) and fermented feed (FF) groups (basal diet supplemented with 2.5, 5.0 and 7.5% FF, respectively). The experimental period lasted 28 days.

Results

The results showed that 5.0 and 7.5% FF groups decreased feed conversion rate (FCR) when compared with the control group (p < 0.05). The 5.0% FF group reduced the activity of alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) in serum; while the 7.5% FF group decreased the concentration of total cholesterol (TC), ALP and LDH activity (p < 0.05). Furthermore, the 7.5% FF group significantly increased total antioxidant capacity (T-AOC) in serum (p < 0.05); 2.5% and 5.0% FF groups significantly increased glutathione peroxidase (GSH-Px) in serum (p < 0.05); all FF groups increased the activity of superoxide dismutase (T-SOD) in serum (p < 0.05). For intestinal health, the villous height and villi/crypt ratio in jejunum were increased in all FF groups, but crypt depth was decreased (p < 0.05); The 5.0% FF groups enhanced T-AOC activity in jejunum (p < 0.05); The 2.5% and 5.0% FF groups enhanced GSH-Px activity (p < 0.05) in jejunum; All FF groups reduced malondialdehyde (MDA) level in jejunum (p < 0.05). LEfSe analysis showed that the cecum microbiota was significantly dominant in the 2.5% FF group compared to the control group including Firmicutes, Lactobacillales, Lactobacillus, and Prevotella; the flora that were significantly dominant in the 5.0% FF group compared to the control group included Bacteroidaceae, Bacteroides, Megamonas, and Prevotella; and the groups that were significantly dominant in the 7.5% FF group compared to the control group included Bacteroidota, Bacteroides, Bacteroidaceae, and Ruminococcaceae.

Discussion

In summary, dietary FF supplementation improved growth performance, serum biochemical parameters and antioxidant capacity of lion-head goslings, as well as improved jejunal tissue morphology and optimized intestinal flora structure. In particular, the FF addition at a dose of 7.5% was relatively more effective for lion- head goslings.

Expression and characterization of recombinant IL-1Ra in Aspergillus oryzae as a system

BACKGROUND

The interleukin-1 receptor antagonist (IL-1Ra) is a crucial molecule that counteracts the effects of interleukin-1 (IL-1) by binding to its receptor. A high concentration of IL-1Ra is required for complete inhibition of IL-1 activity. However, the currently available Escherichia coli-expressed IL-1Ra (E. coli IL-1Ra, Anakinra) has a limited half-life. This study aims to produce a cost-effective, functional IL-1Ra on an industrial scale by expressing it in the pyrG auxotroph Aspergillus oryzae.

RESULTS

We purified A. oryzae-expressed IL-1Ra (Asp. IL-1Ra) using ion exchange and size exclusion chromatography (53 mg/L). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that Asp. IL-1Ra is N-glycosylated and approximately 17 kDa in size. We conducted a comparative study of the bioactivity, binding kinetics, and half-life between Asp. IL-1Ra and E. coli IL-1Ra. Asp. IL-1Ra showed good bioactivity even at a low concentration of 0.5 nM. The in vitro half-life of Asp. IL-1Ra was determined for different time points (0, 24, 48, 72, and 96 h) and showed higher stability than E. coli IL-1Ra, despite exhibiting a 100-fold lower binding affinity (2 nM).

CONCLUSION

This study reports the production of a functional Asp. IL-1Ra with advantageous stability, without extensive downstream processing. To our knowledge, this is the first report of a recombinant functional and stable IL-1Ra expressed in A. oryzae. Our results suggest that Asp. IL-1Ra has potential for industrial-scale production as a cost-effective alternative to E. coli IL-1Ra.

Bioengineered Enzymes and Precision Fermentation in the Food Industry

Enzymes have been used in the food processing industry for many years. However, the use of native enzymes is not conducive to high activity, efficiency, range of substrates, and adaptability to harsh food processing conditions. The advent of enzyme engineering approaches such as rational design, directed evolution, and semi-rational design provided much-needed impetus for tailor-made enzymes with improved or novel catalytic properties. Production of designer enzymes became further refined with the emergence of synthetic biology and gene editing techniques and a plethora of other tools such as artificial intelligence, and computational and bioinformatics analyses which have paved the way for what is referred to as precision fermentation for the production of these designer enzymes more efficiently. With all the technologies available, the bottleneck is now in the scale-up production of these enzymes. There is generally a lack of accessibility thereof of large-scale capabilities and know-how. This review is aimed at highlighting these various enzyme-engineering strategies and the associated scale-up challenges, including safety concerns surrounding genetically modified microorganisms and the use of cell-free systems to circumvent this issue. The use of solid-state fermentation (SSF) is also addressed as a potentially low-cost production system, amenable to customization and employing inexpensive feedstocks as substrate.

Evaluation of wool protein hydrolysate as peptone for production of microbial enzymes

Peptones are one of the most expensive components of microbial culture media. The present study was conducted to test the usability of low-cost sheep wool peptone (SWP) as an organic nitrogen source in the production of six industrially important enzymes (lipase, amylase, tannase, pectinase, cellulase and invertase). SWP was prepared by alkaline hydrolysis and acid neutralization. Bacillus licheniformis and Aspergillus niger were selected as test microorganisms for enzyme production. To evaluate the efficacy of SWP in enzyme production, it was compared with commercial tryptone peptone (TP) in the shaking flask cultures of the test microorganisms. The optimum concentration of both SWP and TP was determined to be 8 g/L for the production of B. licheniformis-derived enzymes, but 6 g/L for the production of A. niger-derived enzymes. It was determined that SWP was superior to TP in the production of four enzymes (lipase, amylase, tannase and pectinase) of both B. licheniformis and A. niger. This is the first study about the usage of sheep wool protein hydrolysate (SWP) as an organic nitrogen source or a peptone in fermentative production of microbial enzymes.

Production of Glucoamylase from Novel Strain of Alternaria Alternata under Solid State Fermentation

Glucoamylase has an essential role as biocatalyst in various important industries of Pakistan. It is synthesized by using various fungal and bacterial strains, and different ecocultural conditions are applied under solid substrate fermentation method (SSF) to get the highest yield of glucoamylase. Alternaria alternata is an important fungus that can grow on industrial raw material like wheat bran, dried potato powder, tea leaves, rice husk, and sugar cane peel which are used as substrate. Among all, dried potato powder (10g) proved the best fermentation media for growth of fungal strain as well as maximum glucoamylase producer. Moreover, several chemical and physical states were also explored through solid substrate fermentation technique on glucoamylase yield. The highest glucoamylase production was recorded after 72 hours incubation in incubation chamber with 10g raw substrate, 1ml inoculum spore solution, 30°C temperature, and 5 pH. Further, phosphate buffer (5 pH) as moistening agent, 5% starch concentration and media additive as nitrogen (yeast extract), and carbon source (maltose) were screened for maximum glucoamylase titer (17.3 ± 0.05a°U/ml/min) and the highest specific activity (39.2U/mg). These cultural conditions were most appropriate for growth of A. alternata on solid media and production of highest glucoamylase under solid state fermentation procedure that could be utilized for commercial synthesis of glucoamylase.

Analysis of Aspergillus versicolor exudate composition

Aspergillus versicolor, a widely distributed fungus, is associated with pollution and carcinogenic hazards. This study aimed to examine the functions of the A. versicolor exudate and laid a scientific foundation for improving our understanding, utilization, and control of A. versicolor. The A. versicolor exudate proteome, ion content, and amino acid components were determined using label-free quantitation, atomic absorption spectrophotometry, and high-performance liquid chromatography, respectively. In total, 502 proteins were identified in the A. versicolor exudate. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and cluster of orthologous group analyses were used to annotate the functional classification and pathways of the aligned proteins. Proteins identified in the exudate were mainly enriched in carbohydrate metabolic process, translation, oxidoreductase activity, oxidoreductase activity, hydrolase activity, cell wall-related processes, catalytic activity, and unknown functions. The exudate comprised Na, K, Ca, Fe, and Mg cations. Among the 17 types of amino acids detected in the exudate, 7 were essential and 10 were nonessential. The exudate may be involved in the vital processes of A. versicolor. Additionally, the exudate may play an important role in the growth, development, reproduction, homeostasis, nutrient supply for regrowth, and virulence of A. versicolor.

Aspergillus Hydrophobins: Physicochemical Properties, Biochemical Properties, and Functions in Solid Polymer Degradation

Hydrophobins are small amphipathic proteins conserved in filamentous fungi. In this review, the properties and functions of Aspergillus hydrophobins are comprehensively discussed on the basis of recent findings. Multiple Aspergillus hydrophobins have been identified and categorized in conventional class I and two non-conventional classes. Some Aspergillus hydrophobins can be purified in a water phase without organic solvents. Class I hydrophobins of Aspergilli self-assemble to form amphipathic membranes. At the air–liquid interface, RolA of Aspergillus oryzae self-assembles via four stages, and its self-assembled films consist of two layers, a rodlet membrane facing air and rod-like structures facing liquid. The self-assembly depends mainly on hydrophobin conformation and solution pH. Cys4–Cys5 and Cys7–Cys8 loops, disulfide bonds, and conserved Cys residues of RodA-like hydrophobins are necessary for self-assembly at the interface and for adsorption to solid surfaces. AfRodA helps Aspergillus fumigatus to evade recognition by the host immune system. RodA-like hydrophobins recruit cutinases to promote the hydrolysis of aliphatic polyesters. This mechanism appears to be conserved in Aspergillus and other filamentous fungi, and may be beneficial for their growth. Aspergilli produce various small secreted proteins (SSPs) including hydrophobins, hydrophobic surface–binding proteins, and effector proteins. Aspergilli may use a wide variety of SSPs to decompose solid polymers.

Fungal Proteases as Emerging Biocatalysts to Meet the Current Challenges and Recent Developments in Biomedical Therapies: An Updated Review

With the increasing world population, demand for industrialization has also increased to fulfill humans' living standards. Fungi are considered a source of essential constituents to produce the biocatalytic enzymes, including amylases, proteases, lipases, and cellulases that contain broad-spectrum industrial and emerging applications. The present review discussed the origin, nature, mechanism of action, emerging aspects of genetic engineering for designing novel proteases, genome editing of fungal strains through CRISPR technology, present challenges and future recommendations of fungal proteases. The emerging evidence revealed that fungal proteases show a protective role to many environmental exposures and discovered that an imbalance of protease inhibitors and proteases in the epithelial barriers leads to the protection of chronic eosinophilic airway inflammation. Moreover, mitoproteases recently were found to execute intense proteolytic processes that are crucial for mitochondrial integrity and homeostasis function, including mitochondrial biogenesis, protein synthesis, and apoptosis. The emerging evidence revealed that CRISPR/Cas9 technology had been successfully developed in various filamentous fungi and higher fungi for editing of specific genes. In addition to medical importance, fungal proteases are extensively used in different industries such as foods to prepare butter, fruits, juices, and cheese, and to increase their shelf life. It is concluded that hydrolysis of proteins in industries is one of the most significant applications of fungal enzymes that led to massive usage of proteomics.

Advances in solid-state fermentation for bioconversion of agricultural wastes to value-added products: Opportunities and challenges

The increase in solid waste has become a common problem and causes environmental pollution worldwide. A green approach to valorise solid waste for sustainable development is required. Agricultural residues are considered suitable for conversion into profitable products through solid-state fermentation (SSF). Agricultural wastes have high organic content that is used as potential substrates to produce value-added products through SSF. The importance of process variables used in solid-phase fermentation is described. The applications of SSF developed products in the food industry as flavouring agents, acidifiers, preservatives and flavour enhancers. SSF produces secondary metabolites and essential enzymes. Wastes from agricultural residues are used as bioremediation agents, biofuels and biocontrol agents through microbial processing. In this review paper, the value addition of agricultural wastes by SSF through green processing is discussed with the current knowledge on the scenarios, sustainability opportunities and future directions of a circular economy for solid waste utilisation.

An Alkalothermophilic Amylopullulanase from the Yeast Clavispora lusitaniae ABS7: Purification, Characterization and Potential Application in Laundry Detergent

In the present study, α-amylase and pullulanase from Clavispora lusitaniae ABS7 isolated from wheat seeds were studied. The gel filtration and ion-exchange chromatography revealed the presence of α-amylase and pullulanase activities in the same fraction with yields of 23.88% and 21.11%, respectively. SDS-PAGE showed a single band (75 kDa), which had both α-amylase (independent of Ca2+) and pullulanase (a calcium metalloenzyme) activities. The products of the enzymatic reaction on pullulan were glucose, maltose, and maltotriose, whereas the conversion of starch produced glucose and maltose. The α-amylase and pullulanase had pH optima at 9 and temperature optima at 75 and 80 °C, respectively. After heat treatment at 100 °C for 180 min, the pullulanase retained 42% of its initial activity, while α-amylase maintained only 38.6%. The cations Zn2+, Cu2+, Na+, and Mn2+ increased the α-amylase activity. Other cations Hg2+, Mg2+, and Ca2+ were stimulators of pullulanase. Urea and Tween 80 inhibited both enzymes, whereas EDTA only inhibited pullulanase. In addition, the amylopullulanase retained its activity in the presence of various commercial laundry detergents. The performance of the alcalothermostable enzyme of Clavispora lusitaniae ABS7 qualified it for the industrial use, particularly in detergents, since it had demonstrated an excellent stability and compatibility with the commercial laundry detergents.

Biotechnology approach using watermelon rind for optimization of α-amylase enzyme production from Trichoderma virens using response surface methodology under solid-state fermentation

Production of amylases by fungi under solid-state fermentation is considered the best methodology for commercial scaling that addresses the ever-escalating needs of the worldwide enzyme market. Here response surface methodology (RSM) was used for the optimization of process variables for α-amylase enzyme production from Trichoderma virens using watermelon rinds (WMR) under solid-state fermentation (SSF). The statistical model included four variables, each detected at two levels, followed by model development with partial purification and characterization of α-amylase. The partially purified α-amylase was characterized with regard to optimum pH, temperature, kinetic constant, and substrate specificity. The results indicated that both pH and moisture content had a significant effect (P < 0.05) on α-amylase production (880 U/g) under optimized process conditions at a 3-day incubation time, moisture content of 50%, 30 °C, and pH 6.98. Statistical optimization using RSM showed R² values of 0.9934, demonstrating the validity of the model. Five α-amylases were separated by using DEAE-Sepharose and characterized with a wide range of optimized pH values (pH 4.5-9.0), temperature optima (40-60 °C), low Km values (2.27-3.3 mg/mL), and high substrate specificity toward large substrates. In conclusion, this study presents an efficient and green approach for utilization of agro-waste for production of the valuable α-amylase enzyme using RSM under SSF. RSM was particularly beneficial for the optimization and analysis of the effective process parameters.

Thalassobacillus, a genus of extreme to moderate environmental halophiles with biotechnological potential

Thalassobacillus is a moderately halophilic genus that has been isolated from several sites worldwide, such as hypersaline lakes, saline soils, salt flats, and volcanic mud. Halophilic bacteria have provided functional stable biomolecules in harsh conditions for industrial purposes. Despite its potential biotechnological applications, Thalassobacillus has not been fully characterized yet. This review describes the Thalassobacillus genus, with the few species reported, pointing out its possible applications in enzymes (amylases, cellulases, xylanases, and others), biosurfactants, bioactive compounds, biofuels production, bioremediation, and plant growth promotion. The Thalassobacillus genus represents a little-explored biological resource but with a high potential.