Optimization of protease production from Bacillus halodurans under solid state fermentation using agrowastes

Stable protease from Bacillus licheniformis-MA1 strain: statistical production optimization, kinetic and thermodynamic characterization, and application in silver recovery from used X-ray films

BACKGROUND

Alkaline proteases are useful enzymes for various industrial applications as bio-additives in detergents and in the recovery of silver from used X-ray films. Therefore, many strategies were used to increase enzyme production and reduce production costs by using microbial cultures, using agro-industrial waste, and improving growth conditions via statistical methods. The enzyme kinetics and thermodynamics were studied as well as its ability to recover silver was also evaluated.

RESULTS

An alkaline protease suitable for industrial applications was produced by Bacillus licheniformis strain-MA1. The ability of B. licheniformis strain-MA1 to produce protease was optimized using multi-factorial designs (Plackett-Burman and Box-Behnken). Optimization process improved enzyme production by 9.6-fold over that obtained from the original medium. Highest alkaline protease production was reached after 72 h at pH 7.0, 35 °C, and 150 rpm. The protease was maximally active at 50 °C and pH 9.0 with high thermal and pH stability. The protease showed high catalytic efficiency and high affinity toward substrate with low activation energy (Ea). In addition, the thermodynamic parameters of protease enzyme (enthalpy, free energy, and entropy) were also investigated and showed its superior thermal stability. At 70 °C the thermal deactivation constant (kd) was 4.75-fold higher than that at 50 °C. The higher t0.5, D-values, and activation energy for thermal denaturation (Ed) of the protease indicated its higher thermal stability and thus its potential application in industrial processes. The compatibility of the protease with laundry detergents at 40 °C was higher than at 50 °C. In the presence of EDTA, the protease enzyme retained 93.6% of its activity. Furthermore, the crude enzyme successfully hydrolyzed the gelatin layer from X-ray films waste after 1 h enabling recycling and reuse.

CONCLUSIONS

Stable alkaline protease from B. licheniformis strain-MA1 was suitable for some industrial aspects as a bio-additive in detergents and capable of recovering silver from used X-ray.

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.

Enhanced Synthesis, Purification, and Characterization of a Marine Bacterial Consortium-Derived Protease Enzyme With Destaining and Keratinolytic Activity

Two marine-derived bacteria, Bacillus paralicheniformis (HR-1) and Bacillus haynesii (HR-5), were isolated from sediments and identified using 16S ribosomal RNA gene amplification and sequencing as well as biochemical analysis. The development of a bacterial consortium (HR-1 & HR-5) from these two bacteria was used to increase the production of the protease enzyme under various conditions, including fermentation media, carbon and nitrogen sources (1% w/v), different pH levels, incubation time, and the obtained enzyme, were detected using SDS-PAGE followed by purification. Bacterial consortium HR-1 & HR-5 exhibited maximum protease production (330.42 ± 4.47 U/mL) than the individual isolates HR-1 (156.32 ± 2.14 U/mL) and HR-5 (185.73 ± 5.14 U/mL) on supplementing peptone (1% w/v), 2.8% skim milk + N-broth, pH 9, and dextrose (1% w/v) after 48 h of incubation time. The purified enzyme showed increased activity at alkaline pH 9.0 and also in the presence of ions such as Ca+2, Fe+3, Mg+2, and Mn+2. The purified protease obtained from the consortium HR-1 and HR-5 shows improved efficiency for stain removal from cloth as well as high keratinolytic efficiency for poultry feather degradation, making this enzyme suitable for industrial use, particularly in the textile and tannery sectors.

Enhanced biocatalytic laccase production using agricultural waste in solid-state fermentation by Aspergillus oryzae for p-chlorophenol degradation

Agricultural residues are one of the most cost-effective and readily accessible carbon resources for producing commercially significant enzymes. Several enzymes have been used in different industries like pharmaceuticals, foods, textiles, and dyes that can be generated by various species of microbes found in waste from agriculture. The current research investigated laccase production by Aspergillus oryzae utilizing agricultural wastes. Physical and chemical properties, including pH, temperature, sucrose, yeast extract, and copper sulfate levels, were optimized. The utilization of the response surface methodology along with the centralized composite design method, which assesses multiple media parameters and utilizes a two-level experimental approach, aids in determining the variable and its significance in increasing production quality. The centralized composite design enhancement showed that the optimal conditions for highest laccase activity (623.16 U/mL) were pH 7.0, temperature 25 °C, corn cobs as substrate, sucrose (2.0 %), yeast extract (1.0 %), and copper sulfate (0.1 mM) level. The laccase enzyme was optimized using various pH, temperature, metal ions, and inhibitors combinations. The extracted laccase enzyme maximum activity was attained at pH 6.0 and 40 °C. The inclusion of divalent ions can enhance laccase activity, while the use of various inhibitors decreases laccase activity. Under various pH circumstances, the Aspergillus oryzae laccase enzyme can successfully degrade p-chlorophenol. The present study describes statistically validated optimal methodologies for enhancing laccase synthesis, leading to a laccase production technique that is simultaneously highly efficient and economically profitable, with possible use of p-chlorophenol degradation.

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.

Optimization of Enzymatic Hydrolysis by Protease Produced from Bacillus subtilis MTCC 2423 to Improve the Functional Properties of Wheat Gluten Hydrolysates

This study is aimed at investigating the reutilizing of gluten protein from the wheat processing industry by Bacillus subtilis MTCC 2423 protease to obtain gluten hydrolysates with high added value. Gluten protein hydrolysis using protease achieved a 34.07% degree of hydrolysis with 5% gluten protein, at a hydrolysis time of 2 h for 1000 U/mL at pH 8.0 and temperature of 40°C. Compared to the wheat gluten, the obtained hydrolysates exhibited enhanced functional attributes, including heightened solubility (43%), increased emulsifying activity (93.08 m2/g), and improved radical scavenging properties. Furthermore, these hydrolysates demonstrated enhanced antioxidant potential, as evidenced by elevated ABTS (2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) of 81.25% and DPPH (2,2-diphenyl-1-picrylhydrazyl) of 56.46% radical scavenging activities and also exhibited a higher α-amylase inhibitory effect of 33.98%. The enhancement in functional characteristics of wheat gluten hydrolysates was observed by Fourier transform infrared spectroscopy. The percentage of free amino acids obtained by protease-mediated hydrolysates increased significantly compared to the unhydrolyzed wheat, which was observed by high-performance liquid chromatography. These findings suggest that wheat gluten hydrolysates hold promising potential as functional and nutritional food ingredients in the food industry, owing to their enhanced functionalities and potential antioxidant and antidiabetic properties.

Coproduction of alkaline protease and xylanase from genetically modified Indonesian local Bacillus halodurans CM1 using corncob as an inducing substrate

The production of corn generates a substantial amount of agro-industrial waste, with corncob accounting for a significant portion of this waste. In this study, we focused on utilizing corncob as a carbon source and inducer to simultaneously produce two valuable industrial enzymes, protease, and xylanase, using a recombinant strain of B. halodurans CM1. Interestingly, xylan-rich corncob not only enhanced the xylanase activity but also induced protease activity of the modified B. halodurans CM1 strain. The effect of corncob concentration on the coproduction of protease and xylanase was investigated. Corncob with 6 % concentration induced protease activity of 1020.7 U/mL and xylanase activity of 502.8 U/mL in a 7 L bioreactor under the condition of 1 vvm aeration, 250 rpm agitation, 37 °C temperature, initial pH 9.0, and 40 h incubation period. The protease produced was an alkalothermophilic enzyme whose highest activity was at pH 12 and 50 °C, and it belonged to a serine protease family. This alkalothermophilic protease's activity to some degree was reduced by Co2+, Mg2+, Fe2+, Zn2+, and K+, but enhanced by Ca2+ and Ni2+ (at 5 mM). The protease was stable even under the presence of a 15 % concentration of acetone, DMSO, ethanol, and isopropyl alcohol. The protease activity at 30 °C was not considerably changed by the presence of detergent, indicating excellent potential as a washing detergent additive. According to these findings, corncob has the potential to be a substrate for the coproduction of protease and xylanase, which have a wide range of industrial uses.

A scientific version of understanding "Why did the chickens cross the road"? - A guided journey through Bacillus spp. towards sustainable agriculture, circular economy and biofortification

The world, a famished planet with an overgrowing population, requires enormous food crops. This scenario compelled the farmers to use a high quantity of synthetic fertilizers for high food crop productivity. However, prolonged usage of chemical fertilizers results in severe adverse effects on soil and water quality. On the other hand, the growing population significantly consumes large quantities of poultry meats. Eventually, this produces a mammoth amount of poultry waste, chicken feathers. Owing to the protein value of the chicken feathers, these wastes are converted into protein hydrolysate and further extend their application as biostimulants for sustained agriculture. The protein profile of chicken feather protein hydrolysate (CFPH) produced through Bacillus spp. was the maximum compared to physical and chemical protein extraction methods. Several studies proved that the application of CFPH and active Bacillus spp. culture to soil and plants results in enhanced plant growth, phytochemical constituents, crop yield, soil nutrients, fertility, microbiome and resistance against diverse abiotic and biotic stresses. Overall, "CFPH - Jack of all trades" and "Bacillus spp. - an active camouflage to the surroundings where they applied showed profound and significant benefits to the plant growth under the most adverse conditions. In addition, Bacillus spp. coheres the biofortification process in plants through the breakdown of metals into metal ions that eventually increase the nutrient value of the food crops. However, detailed information on them is missing. This can be overcome by further real-world studies on rhizoengineering through a multi-omics approach and their interaction with plants. This review has explored the best possible and efficient strategy for managing chicken feather wastes into protein-rich CFPH through Bacillus spp. bioconversion and utilizing the CFPH and Bacillus spp. as biostimulants, biofertilizers, biopesticides and biofortificants. This paper is an excellent report on organic waste management, circular economy and sustainable agriculture research frontier.

Chicken viscera meal as substrate for the simultaneous production of antioxidant compounds and proteases by Aspergillus oryzae

The use of chicken waste can contribute to the development of new processes and obtaining molecules with high added value. An experimental design was applied to evaluate the effect of moisture, temperature, and inoculum size on the production of antioxidant peptides and proteases by A. oryzae IOC3999 through solid-state fermentation (SSF) of chicken viscera meal. As a result, the process conditions strongly influenced protease production and antioxidant activity of the fermented products. A global analysis of the results indicated that the most adequate conditions for SSF were (assay 9): 40% initial moisture, 30 °C as the incubation temperature, 5.05 × 106 spores/g as the inoculum size, and 48-h fermentation as the fermentation time. Under this condition, the antioxidant activities for the ABTS- and DPPH-radicals inhibition and ferric reducing antioxidant power (FRAP) methods were 376.16, 153.29, and 300.47 (µmol TE/g), respectively, and the protease production reached 428.22 U/g. Ultrafiltration of the crude extract obtained under optimized fermentation conditions was performed, and the fraction containing peptides with molecular mass lower than 3 kDa showed the highest antioxidant activity. The proteases were biochemically characterized and showed maximal activity at pH values ranging from 5.0 to 6.0 and a temperature of 50 °C. The thermodynamic parameters indicated that the process of thermal protease inactivation is not spontaneous (ΔG*d > 88.78 kJ/mol), increasing with temperature (ΔH*d 27.01-26.88 kJ/mol), and with reduced disorder in the system (ΔS*d <  - 197.74 kJ/mol) probably caused by agglomeration of partially denatured enzymes.

Optimization of subtilisin production from Bacillus subtilis strain ZK3 and biological and molecular characterization of synthesized subtilisin capped nanoparticles

The increase and dissemination of multi-drug resistant bacteria have presented a major healthcare challenge, making bacterial infections a significant concern. The present research contributes towards the production of bioactive subtilisin from a marine soil isolate Bacillus subtilis strain ZK3. Custard apple seed powder (raw carbon) and mustard oil cake (raw nitrogen) sources showed a pronounced effect on subtilisin production. A 7.67-fold enhancement in the production was evidenced after optimization with central composite design-response surface methodology. Subtilisin capped silver (AgNP) and zinc oxide (ZnONP) nanoparticles were synthesized and characterized by UV-Visible spectroscopy. Subtilisin and its respective nanoparticles revealed significant biological properties such as, antibacterial activity against all tested pathogenic strains with potential against Escherichia coli and Pseudomonas aeruginosa. Prospective antioxidant behavior of subtilisin, AgNP and ZnONP was evidenced through radical scavenging assays with ABTS and DPPH. Subtilisin, AgNP and ZnONP revealed cytotoxic effect against cancerous breast cell lines MCF-7 with IC50of 83.48, 3.62 and 7.57 µg/mL respectively. Characterizations of nanoparticles were carried out by Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray, X-ray diffraction, thermogravimetric analysis and atomic force microscopy analysis to elucidate the structure, surface and thermostability properties. The study proposes the potential therapeutic applications of subtilisin and its nanoparticles, a way forward for further exploration in the field of healthcare.

Screening of marine sediment-derived microorganisms and their bioactive metabolites: a review

Marine sediments are one of the largest habitats on Earth, and their unique ecology, such as high salinity, high pressure, and hypoxia, may activate certain silent genes in marine microbes, resulting in microbes, enzymes, active products, and specific metabolic pathways that can adapt to these specific ecological environments. Marine sediment-derived microorganisms and their bioactive metabolites are of great significance and have potential commercial development prospects for food, pharmaceutical, chemical industries, agriculture, environmental protection and human nutrition and health. In recent years, although there have been numerous scientific reports surrounding marine sediment-derived microorganisms and their bioactive metabolites, a comprehensive review of their research progress is lacking. This paper presents the development and renewal of traditional culture-dependent and omics analysis techniques and their application to the screening of marine sediment-derived microorganisms producing bioactive substances. It also highlights recent research advances in the last five years surrounding the types, functional properties and potential applications of bioactive metabolites produced by marine sediment-derived microorganisms. These bioactive metabolites mainly include antibiotics, enzymes, enzyme inhibitors, sugars, proteins, peptides, and some other small molecule metabolites. In addition, the review ends with concluding remarks on the challenges and future directions for marine sediment-derived microorganisms and their bioactive metabolites. The review report not only helps to deepen the understanding of marine sediment-derived microorganisms and their bioactive metabolites, but also provides some useful information for the exploitation and utilization of marine microbial resources and the mining of new compounds with potential functional properties.

Optimized production of keratinolytic proteases from Bacillus tropicus LS27 and its application as a sustainable alternative for dehairing, destaining and metal recovery

The present study describes the isolation and characterization of Bacillus tropicus LS27 capable of keratinolytic protease production from Russell Market, Shivajinagar, Bangalore, Karnataka, with its diverse application. The ability of this strain to hydrolyze chicken feathers and skim milk was used to assess its keratinolytic and proteolytic properties. The strain identification was done using biochemical and molecular characterization using the 16S rRNA sequencing method. Further a sequential and systematic optimization of the factors affecting the keratinase production was done by initially sorting out the most influential factors (NaCl concentration, pH, inoculum level and incubation period in this study) through one factor at a time approach followed by central composite design based response surface methodology to enhance the keratinase production. Under optimized levels of NaCl (0.55 g/L), pH (7.35), inoculum level (5%) and incubation period (84 h), the keratinase production was enhanced from 41.62 U/mL to 401.67 ± 9.23 U/mL (9.65 fold increase) that corresponds to a feather degradation of 32.67 ± 1.36% was achieved. With regard to the cost effectiveness of application studies, the crude enzyme extracted from the optimized medium was tested for its potential dehairing, destaining and metal recovery properties. Complete dehairing was achieved within 48 h of treatment with crude enzyme without any visible damage to the collagen layer of goat skin. In destaining studies, combination of crude enzyme and detergent solution [1 mL detergent solution (5 mg/mL) and 1 mL crude enzyme] was found to be most effective in removing blood stains from cotton cloth. Silver recovery from used X-ray films was achieved within 6 min of treatment with crude enzyme maintained at 40 °C.

Agro-Industrial Food Waste as a Low-Cost Substrate for Sustainable Production of Industrial Enzymes: A Critical Review

The grave environmental, social, and economic concerns over the unprecedented exploitation of non-renewable energy resources have drawn the attention of policy makers and research organizations towards the sustainable use of agro-industrial food and crop wastes. Enzymes are versatile biocatalysts with immense potential to transform the food industry and lignocellulosic biorefineries. Microbial enzymes offer cleaner and greener solutions to produce fine chemicals and compounds. The production of industrially important enzymes from abundantly present agro-industrial food waste offers economic solutions for the commercial production of value-added chemicals. The recent developments in biocatalytic systems are designed to either increase the catalytic capability of the commercial enzymes or create new enzymes with distinctive properties. The limitations of low catalytic efficiency and enzyme denaturation in ambient conditions can be mitigated by employing diverse and inexpensive immobilization carriers, such as agro-food based materials, biopolymers, and nanomaterials. Moreover, revolutionary protein engineering tools help in designing and constructing tailored enzymes with improved substrate specificity, catalytic activity, stability, and reaction product inhibition. This review discusses the recent developments in the production of essential industrial enzymes from agro-industrial food trash and the application of low-cost immobilization and enzyme engineering approaches for sustainable development.

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.