Microbial proteases and their applications

A hyperstable, low-salt adapted protease from halophilic archaeon with potential applications in salt-fermented foods

Salt-tolerant proteases with remarkable stability are highly desirable biocatalysts in the salt-fermented food industry. In this study, the undigested autocleavage product of HlyA (halolysin A), a low-salt adapted halolysin from halophilic archaeon Halococcus salifodinae, was investigated. HlyA underwent autocleavage of its C-terminal extension (CTE) at temperatures over 40 °C or NaCl concentrations below 2 M to yield HlyAΔCTE. HlyAΔCTE demonstrated robust stability over a wide range of -20-60 °C, 0.5-4 M NaCl, and pH 6.0-10.0 for at least 72 h. Notably, HlyAΔCTE is the first reported halolysin with such exceptional stability. Compared with HlyA, HlyAΔCTE preferred high temperatures (50-75 °C), low salinities (0.5-2.5 M NaCl), and near-neutral (pH 6.5-8.0) conditions to achieve high activity, consistently with its production conditions. HlyAΔCTE displayed a higher Vmax value against azocasein than HlyA. During fish sauce fermentation, HlyAΔCTE significantly enhanced fish protein hydrolysis, indicating its potential as a robust biocatalyst in the salt-fermented food industry.

In silico and experimental characterization of a new polyextremophilic subtilisin-like protease from Microbacterium metallidurans and its application as a laundry detergent additive

Considering the current growing interest in new and improved enzymes for use in a variety of applications, the present study aimed to characterize a novel detergent-stable serine alkaline protease from the extremophilic actinobacterium Microbacterium metallidurans TL13 (MmSP) using a combined in silico and experimental approach. The MmSP showed a close phylogenetic relationship with high molecular weight S8 peptidases of Microbacterium species. Moreover, its physical and chemical parameters computed using Expasy's ProtParam tool revealed that MmSP is hydrophilic, halophilic and thermo-alkali stable. 3D structure modelling and functional prediction of TL13 serine protease resulted in the detection of five characteristic domains: [catalytic subtilase domain, fibronectin (Fn) type-III domain, peptidase inhibitor I9, protease-associated (PA) domain and bacterial Ig-like domain (group 3)], as well as the three amino acid residues [aspartate (D182), histidine (H272) and serine (S604)] in the catalytic subtilase domain. The extremophilic strain TL13 was tested for protease production using agricultural wastes/by-products as carbon substrates. Maximum enzyme activity (390 U/gds) was obtained at 8th day fermentation on potato peel medium. Extracellular extract was concentrated and partially purified using ammonium sulfate precipitation methodology (1.58 folds purification fold). The optimal pH, temperature and salinity of MmSP were 9, 60 °C and 1 M NaCl, respectively. The MmSP protease showed broad pH stability, thermal stability, salt tolerance and detergent compatibility. In order to achieve the maximum stain removal efficacy by the TL 13 serine protease, the operation conditions were optimized using a Box-Behnken Design (BBD) with four variables, namely, time (15-75 min), temperature (30-60 °C), MmSP enzyme concentration (5-10 U/mL) and pH (7-11). The maximum stain removal yield (95 ± 4%) obtained under the optimal enzymatic operation conditions (treatment with 7.5 U/mL of MmSP during 30 min at 32 °C and pH9) was in good agreement with the value predicted by the regression model (98 ± %), which prove the validity of the fitted model. In conclusion, MmSP appears to be a good candidate for industrial applications, particularly in laundry detergent formulations, due to its high hydrophilicity, alkali-halo-stability, detergent compatibility and stain removal efficiency.

Tailoring the specificity of ficin versus large hemoglobin and small casein by co-immobilizing inert proteins on the immobilized enzyme layer and further modification with aldehyde dextran

Ficin has been immobilized at full loading on glyoxyl agarose beads. Then, ficin was blocked with 2,2'-dipyridyldisulfide. To be effective, the modification must be performed in the presence of 0.5 M urea, as the enzyme was not inhibited under standard conditions, very likely because the catalytic Cys was not fully exposed to the medium. Activity could be fully recovered by incubation with 1 M mercaptoethanol. This biocatalyst could hydrolyze hemoglobin and casein. The objective of this paper was to increase the enzyme specificity versus small proteins by generating steric hindrances to the access of large proteins. The step by step blocking via ionic exchange of the biocatalyst with aminated bovine serum albumin (BSA), aldehyde dextran and a second layer of aminated BSA produced a biocatalyst that maintained its activity versus small synthetic substrates, increased the biocatalyst stability, while reduced its activity to over 50 % versus casein. Interestingly, this treatment almost fully annulled the activity versus hemoglobin, more effectively at 37 °C than at 55 °C. The biocatalyst could be reused 5 times without changes in activity. The changes could be caused by steric hindrances, but it cannot be discarded some changes in enzyme sequence specificity caused by the modifications.

Support Enzyme Loading Influences the Effect of Aldehyde Dextran Modification on the Specificity of Immobilized Ficin for Large Proteins

It has been reported that the modification of immobilized glyoxyl-ficin with aldehyde dextran can promote steric hindrances that greatly reduce the activity of the immobilized protease against hemoglobin, while the protease still maintained a reasonable level of activity against casein. In this paper, we studied if this effect may be different depending on the amount of ficin loaded on the support. For this purpose, both the moderately loaded and the overloaded glyoxyl-ficin biocatalysts were prepared and modified with aldehyde dextran. While the moderately loaded biocatalyst had a significantly reduced activity, mainly against hemoglobin, the activity of the overloaded biocatalyst was almost maintained. This suggests that aldehyde dextran was able to modify areas of the moderately loaded enzyme that were not available when the enzyme was overloaded. This modification promoted a significant increase in biocatalyst stability for both biocatalysts, but the stability was higher for the overloaded biocatalyst (perhaps due to a combination of inter- and intramolecular crosslinking).

Harnessing the potential of microbial keratinases for bioconversion of keratin waste

The increasing global consumption of poultry meat has led to the generation of a vast quantity of feather keratin waste daily, posing significant environmental challenges due to improper disposal methods. A growing focus is on utilizing keratinous polymeric waste, amounting to millions of tons annually. Keratins are biochemically rigid, fibrous, recalcitrant, physiologically insoluble, and resistant to most common proteolytic enzymes. Microbial biodegradation of feather keratin provides a viable solution for augmenting feather waste's nutritional value while mitigating environmental contamination. This approach offers an alternative to traditional physical and chemical treatments. This review focuses on the recent findings and work trends in the field of keratin degradation by microorganisms (bacteria, actinomycetes, and fungi) via keratinolytic and proteolytic enzymes, as well as the limitations and challenges encountered due to the low thermal stability of keratinase, and degradation in the complex environmental conditions. Therefore, recent biotechnological interventions such as designing novel keratinase with high keratinolytic activity, thermostability, and binding affinity have been elaborated here. Enhancing protein structural rigidity through critical engineering approaches, such as rational design, has shown promise in improving the thermal stability of proteins. Concurrently, metagenomic annotation offers insights into the genetic foundations of keratin breakdown, primarily predicting metabolic potential and identifying probable keratinases. This may extend the understanding of microbial keratinolytic mechanisms in a complex community, recognizing the significance of synergistic interactions, which could be further utilized in optimizing industrial keratin degradation processes.

Sour orange (Citrus aurantium) seed, a rich source of protein isolate and hydrolysate - A thorough investigation

Sour orange (Citrus aurantium) seeds are typically discarded by juice processors as waste. This study aimed to extract protein isolates, produce hydrolysates from de-oiled sour orange seeds (SOS), and characterize their physicochemical properties. Previous studies have described methods to obtain protein isolates and hydrolysates from agricultural residues. However, there is limited data on the SOS. This research characterized protein isolates and hydrolysates from SOS, emphasizing yield, purity, and amino acid composition. Protein isolates were extracted using borate saline buffer, saline, and distilled water. Enzymatically hydrolysis was conducted using Protamex® (a commercial protease) at concentrations ranging from 0.2 to 5 g enzyme/100g protein isolate. Differential scanning calorimetry, electrophoresis, and FT-IR spectroscopy were utilized to characterize the isolates and hydrolysates. Data showed that using 5 % saline resulted in protein extraction with a yield and purity of 30 and 86 %, respectively. DSC analysis revealed that the denaturation temperature of the protein isolate was 68 °C, while the hydrolysates exhibited structural instability, as indicated by a decrease in enthalpy change compared to the isolate. The protein isolate had a 76° contact angle. The amino acid profile showed a significant presence of glutamic acid (130.530 mg/g) and arginine (70.210 mg/g). Electrophoresis analysis exhibited four major bands of the protein. The bands' intensity decreased, and new bands appeared after hydrolysis. The enzyme hydrolysis was confirmed using the O-phthaldialdehyde method and FTIR. Findings revealed that based on the free amine group quantity, the hydrolysate obtained using 5 g enzyme/100g protein isolate was 14.220 ± 0.299 μmol/mg protein. The study concluded that sour orange seeds are a good source of protein, with protein isolates and hydrolysates exhibiting desirable characteristics. More research needs to be conducted to acquire further information about their functional properties and potential applications.

Microbial communities in the Dead Sea and their potential biotechnological applications

The Dead Sea is unique compared to other extreme halophilic habitats. Its salinity exceeds 34%, and it is getting saltier. The Dead Sea environment is characterized by a dominance of divalent cations, with magnesium chloride (MgCl2) levels approaching the predicted 2.3 M upper limit for life, an acidic pH of 6.0, and high levels of absorbed ultraviolet radiation. Consequently, only organisms adapted to such a polyextreme environment can survive in the surface, sinkholes, sediments, muds, and underwater springs of the Dead Sea. Metagenomic sequence analysis and amino acid profiling indicated that the Dead Sea is predominantly composed of halophiles that have various adaptation mechanisms and produce metabolites that can be utilized for biotechnological purposes. A variety of products have been obtained from halophilic microorganisms isolated from the Dead Sea, such as antimicrobials, bioplastics, biofuels, extremozymes, retinal proteins, colored pigments, exopolysaccharides, and compatible solutes. These resources find applications in agriculture, food, biofuel production, industry, and bioremediation for the detoxification of wastewater and soil. Utilizing halophiles as a bioprocessing platform offers advantages such as reduced energy consumption, decreased freshwater demand, minimized capital investment, and continuous production.

The role of the gut microbiome in disorders of gut-brain interaction

Disorders of Gut-Brain Interaction (DGBI) are widely prevalent and commonly encountered in gastroenterology practice. While several peripheral and central mechanisms have been implicated in the pathogenesis of DGBI, a recent body of work suggests an important role for the gut microbiome. In this review, we highlight how gut microbiota and their metabolites affect physiologic changes underlying symptoms in DGBI, with a particular focus on their mechanistic influence on GI transit, visceral sensitivity, intestinal barrier function and secretion, and CNS processing. This review emphasizes the complexity of local and distant effects of microbial metabolites on physiological function, influenced by factors such as metabolite concentration, duration of metabolite exposure, receptor location, host genetics, and underlying disease state. Large-scale in vitro work has elucidated interactions between host receptors and the microbial metabolome but there is a need for future research to integrate such preclinical findings with clinical studies. The development of novel, targeted therapeutic strategies for DGBI hinges on a deeper understanding of these metabolite-host interactions, offering exciting possibilities for the future of treatment of DGBI.

Partitioning purification, biochemical characterization, and milk coagulation efficiency of protease from a newly Streptomyces sp. isolate

An actinobacteria strain was isolated from an olive waste mill and tested for protease production on skimmed milk media. The strain identification was achieved through both 16 S rDNA sequencing and phenotypic characterization. The enzyme was purified using the ammonium sulfate/t-butanol three-phase partitioning (TPP) method, followed by characterization to investigate the effect of pH, temperature, and various chemical agents. Subsequently, the enzyme was assessed for its milk coagulation activity. The strain belonging to the Streptomyces genera, exhibits significant phylogenetic and phenotypic differences from the aligned species, suggesting its novelty as a new strain. The enzyme was best separated in the TPP aqueous phase with a 5.35 fold and 56.25% yield. Optimal activity was observed at pH 9.0 and 60 °C, with more than half of the activity retained within the pH range of 7-10 over one hour. The protease demonstrated complete stability between 30 and 60 °C. While metallic ions enhanced enzyme activity, EDTA acted as an inhibitor. The enzyme displayed resistance to H2O2, SDS, Tween 80, and Triton X-100. Notably, it was activated in organic solvents (ethyl acetate, petroleum ether, and xylene), maintaining > 75% of its original activity in butanol, ethanol, and methanol. Additionally, the enzyme yielded high milk coagulant activity of 11,478 SU/mL. The new Streptomyces sp. protease revealed high activity and stability under a wide range of biochemical conditions. Its use in the dairy industry appears particularly promising. Further industrial process investigations will be valuable in determining potential uses for this enzyme.

Screening signal peptidase based on split-GFP assembly technology to promote the secretion of alkaline protease AprE in Bacillus amyloliquefaciens

Improving the ability of bacteria to secrete protein is essential for large-scale production of food enzymes. However, due to the lack of effective tracking technology for target proteins, the optimization of the secretory system is facing many problems. In this study, we utilized the split-GFP system to achieve self-assembly into mature GFP in Bacillus amyloliquefaciens and successfully tracked the alkaline protease AprE. The split-GFP system was employed to assess the signal peptidases, a crucial component in the secretory system, and signal peptidase sipA was identified as playing a role in the secretion of AprE. Deletion of sipA resulted in a higher accumulation of the precursor protein of AprE compared to other signal peptidase deletion strains. To explore the mechanism of signal peptidase on signal peptide, molecular docking and calculation of free energy were performed. The action strength of the signal peptidase is determined by its binding affinity with the tripeptides at the C-terminal of the signal peptide. The functions of signal peptides YdbK and NucB rely on sipA, and overexpression of sipA by integrating it into genome of B. amyloliquefaciens increased the activity of extracellular AprE by 19.9 %. These findings provide insights into enhancing the secretion efficiency of chassis strains.

Endophyte-mediated enhancement of salt resistance in Arachis hypogaea L. by regulation of osmotic stress and plant defense-related genes

Introduction

Soil salinization poses a significant environmental challenge affecting plant growth and agricultural sustainability. This study explores the potential of salt-tolerant endophytes to mitigate the adverse effects of soil salinization, emphasizing their impact on the development and resistance of Arachis hypogaea L. (peanuts).

Methods

The diversity of culturable plant endophytic bacteria associated with Miscanthus lutarioriparius was investigated. The study focused on the effects of Bacillus tequilensis, Staphylococcus epidermidis, and Bacillus siamensis on the development and germination of A. hypogaea seeds in pots subjected to high NaCl concentrations (200 mM L-1).

Results

Under elevated NaCl concentrations, the inoculation of endophytes significantly (p < 0.05) enhanced seedling germination and increased the activities of enzymes such as Superoxide dismutase, catalase, and polyphenol oxidase, while reducing malondialdehyde and peroxidase levels. Additionally, endophyte inoculation resulted in increased root surface area, plant height, biomass contents, and leaf surface area of peanuts under NaCl stress. Transcriptome data revealed an augmented defense and resistance response induced by the applied endophyte (B. tequilensis, S. epidermidis, and B. siamensis) strain, including upregulation of abiotic stress related mechanisms such as fat metabolism, hormones, and glycosyl inositol phosphorylceramide (Na+ receptor). Na+ receptor under salt stress gate Ca2+ influx channels in plants. Notably, the synthesis of secondary metabolites, especially genes related to terpene and phenylpropanoid pathways, was highly regulated.

Conclusion

The inoculated endophytes played a possible role in enhancing salt tolerance in peanuts. Future investigations should explore protein-protein interactions between plants and endophytes to unravel the mechanisms underlying endophyte-mediated salt resistance in plants.

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.

Statistical versus neural network-embedded swarm intelligence optimization of a metallo-neutral-protease production: activity kinetics and food industry applications

An integrated approach involving response surface methodology (RSM) and artificial neural network-ant-colony hybrid optimization (ANN-ACO) was adopted to develop a bioprocess medium to increase the yield of Bacillus cereus neutral protease under submerged fermentation conditions. The ANN-ACO model was comparatively superior (predicted r2 = 98.5%, mean squared error [MSE] = 0.0353) to RSM model (predicted r2 = 86.4%, MSE = 23.85) in predictive capability arising from its low performance error. The hybrid model recommended a medium containing (gL-1) molasses 45.00, urea 9.81, casein 25.45, Ca2+ 1.23, Zn2+ 0.021, Mn2+ 0.020, and 4.45% (vv-1) inoculum, for a 6.75-fold increase in protease activity from a baseline of 76.63 UmL-1. Yield was further increased in a 5-L bioreactor to a final volumetric productivity of 3.472 mg(Lh)-1. The 10.0-fold purified 46.6-kDa-enzyme had maximum activity at pH 6.5, 45-55 °C, with Km of 6.92 mM, Vmax of 769.23 µmolmL-1 min-1, kcat of 28.49 s-1, and kcat/Km of 4.117 × 103 M-1 s-1, at 45 °C, pH 6.5. The enzyme was stabilized by Ca2+, activated by Zn2+ but inhibited by EDTA suggesting that it was a metallo-protease. The biomolecule significantly clarified orange and pineapple juices indicating its food industry application.

Stable and effective eco-enzyme cocktails in powder and liquid form of Stachybotrys microspora used as detergent additives

Objective

The present work aims to optimize fermentation parameters for the simultaneous production of eco-enzymes: proteases, amylases, and endoglucanases from the same fungus Stachybotrys microspora, and to evaluate their stability in free form and formulated in lye as detergent additives.

Methods

Initially, enzyme cocktail production was assayed in a medium comprising inexpensive waste biomass. Using the best substrate, we investigated the effect of its different concentrations and the NaCl concentration on the three enzymes co-production. Next, we studied the effect of several additives on the storage stability of the lyophilized enzyme cocktail (powder in liquid forms) free and incorporated in commercial laundry detergent. Finally, the washing efficiency analysis of the newly formulated enzyme cocktail was evaluated on dirty tissue pieces with different stains.

Results

The highest enzymatic cocktail production was achieved at 30 °C for 96 h after adding 0.1% NaCl and 1.5% wheat bran as waste biomass in the basal culture medium. The effect of adding maltodextrin, sucrose, or polyethylene glycol 4000 during freeze-drying showed that maltodextrin is the best additive to protect the activities of proteases, amylases, and cellulases of liquid and powder enzyme form. Additionally, the liquid formulation of these enzymes showed excellent stability and compatibility with 1% maltodextrin and 10% glycerol. Interestingly, we have developed a new formulation of an enzyme cocktail (liquid and powder) stable and highly compatible with detergents. Comparing the washing performance of different formulations containing our enzyme cocktail to commercial ones showed significantly better removal of different types of stains.

Conclusions

This research shows a cost-effective approach to simultaneously produce proteases, amylases, and endoglucanases from Stachybotrys microspora that could be considered a compatible detergent additive in the green detergent industry.

Collateral beauty in the damages: an overview of cosmetics and therapeutic applications of microbial proteases

Microbial proteases are enzymes secreted by a variety of microorganisms, including bacteria and fungi, and have attracted significant attention due to their versatile applications in the food and pharmaceutical industries. In addition, certain proteases have been used in the development of skin health products and cosmetics. This article provides a review of microbial proteases in terms of their classification, sources, properties, and applications. Moreover, different pharmacological and molecular investigations have been reviewed. Various biological activities of microbial proteases, such as Arazyme, collagenase, elastin, and Nattokinase, which are involved in the digestion of dietary proteins, as well as their potential anti-inflammatory, anti-cancer, antithrombotic, and immunomodulatory effects have been included. Furthermore, their ability to control infections and treat various disorders has been discussed. Finally, this review highlights the potential applications and future perspectives of microbial proteases in biotechnology and biomedicine, and proposes further studies to develop new perspectives for disease control and health-promoting strategies using microbial resources.