Biochemical properties and repression studies of an alkaline serine protease from a haloalkaliphilic actinomycete, Nocardiopsis dassonvillei subsp. albirubida OK-14

Purification, characterization, structural elucidation, and industrial applications of thermostable alkaline protease produced by seaweed-associated Nocardiopsis dassonvillei strain VCs-4

Alkaline proteases are crucial in the enzyme industry. The seaweed-associated strain Nocardiopsis dassonvillei strain VCs-4 produced a protease with the optimal activity of 362.97 U/mL under haloalkaliphilic conditions. Kinetic analysis revealed a Km of 0.17 mg/mL, Vmax of 1928 U/mL/min, and Kcat of 16.66 s-1. The VCs-4 protease showed remarkable stability against chemical stresses, including surfactants, detergents, and bleaching agents, making it suitable for industrial use. Its thermal stability was demonstrated with a ΔH* of 73.36 kJ/mol, ΔS* of -87.27 J/mol, and a half-life (t₁/₂) of 15 min at 80 °C, extended to 19 min in 2 M NaCl. Structural analysis using FTIR and CD spectroscopy revealed a predominance of α-helices (79.64 %) and minimal β-strands (0.55 %) at 60 °C. Additionally, 97.78 % of the residues were in the most preferred regions of the Ramachandran plot, reflecting high stereochemical quality. The enzyme composition includes 17 % cysteine and 8.5 % serine residues, with a charge profile of four negatively charged (Asp, Glu) and seven positively charged (Arg, Lys) residues. The VCs-4 protease demonstrated potential for industrial applications, successfully removing blood stains and hydrolyzing gelatin from used X-ray film.

Keratinous bioresources: their generation, microbial degradation, and value enhancement for biotechnological applications

Keratin is an important bioresource primarily found in feathers, hair, wool, nails, claws, hooves, horns, and beaks. These crucial protein sources are utilized in many ways for diverse applications. The peptides of keratin develop hierarchical complexity, which leads to the formation of these recalcitrant biomasses. Therefore, microbial breakdown of keratin is a complex process and involves important proteolytic enzymes and inorganic factors. Disulfide bond reduction is the key step in keratin degradation that is mainly facilitated by disulfide-reducing agents or disulfide reductases. Notably, α- and β-keratinous substrates exhibit different structural features; as a result, their disintegration processes make a diversity among keratinous biomass. Various studies have suggested that pretreatment can improve degradation yield following microbial processes. Keratin hydrolysates have been investigated for various uses that contribute to mitigating the environmental impact of these solid wastes. Furthermore, keratin peptides possess bioactive properties, including antioxidant, cytoprotective, and anticancer effects, making them potential candidates for biomedical and nutritional sectors. Microbial keratinases are known for a wide range of substrate specificity that significantly contributes to areas like prion decontamination, carcass processing, antimicrobial functions, and skin exfoliation. This review aims to examine keratin bioresources, their structure, and microbial mechanisms for keratin degradation, along with current insights and future applications of keratin hydrolysates and keratinases.

Walnut protein isolate based emulsion as a promising delivery system enhanced lutein bioaccessibility

Lutein, a natural pigment with multiple beneficial bioactivities, faces limitations in food processing due to its instability. In this study, we constructed four modified walnut protein isolate (WNPI) based emulsions as emulsion-based delivery systems (EBDS) for lutein fortification. The modification treatments enhanced the encapsulation efficiency of the WNPI-based EBDS on lutein. The modified WNPI-based EBDS exhibited improved storage and digestive stability, as well as increased lutein delivery capability in simulated gastrointestinal conditions. After in vitro digestion, the lutein retention in the modified WNPI-based EBDS was higher than in the untreated WNPI-based EBDS, with a maximum retention of 49.67 ± 1.10 % achieved after ultrasonic modification. Furthermore, the modified WNPI-based EBDS exhibited an elevated lutein bioaccessibility, reaching a maximum value of 40.49 ± 1.29 % after ultrasonic modification, nearly twice as high as the untreated WNPI-based EBDS. Molecular docking analysis indicated a robust affinity between WNPI and lutein, involving hydrogen bonds and hydrophobic interactions. Collectively, this study broadens WNPI's application and provides a foundation for fortifying other fat-soluble bioactive substances.

Efficacy of the Fruit and Vegetable Peels as Substrates for the Growth and Production of α-Amylases in Marine Actinobacteria

Enzymes from haloalkaliphilic microorganisms have recently focused attention on their potential and suitability in various applications. In this study, the growth and production of extracellular amylases in the marine actinomycetes, using kitchen waste as the raw starch source, have been investigated. Actinobacteria were isolated from the seawater of the Kachhighadi Coast near Dwarika, Gujarat. Seven Actinobacterial isolates of pre-monsoon, monsoon, and post-monsoon seasons belonging to different strains of Nocardiopsis genera were screened and selected for amylase production. The amylase production was initially assessed on the solid media supplemented with the extracts of different fruits and vegetable peels as a substrate by agar plate assay. The strains Kh-2(13), Kh-2(1), and Kh-3(12) produced maximum amylase with potato peel as a substrate, while no significant differences were found with the media containing other peels. Nevertheless, all strains produced amylases at a significant level with other raw substrates as well. For the optimization of the growth and enzyme production, the selected two isolates Kh-2(13) and Kh-3(12) of the monsoon and winter seasons were cultivated in a liquid medium under the submerged fermentation conditions, with potato peel as a substrate. In both organisms, the optimum amylase production was observed in the stationary phase of growth. For amylase production, the effect of different physical and chemical parameters was evaluated. The optimum growth and amylase production was achieved in 2% inoculum size, at pH 8.0, 28℃, and 5% salt concentration. On the basis of the amylase production index (API) (a ratio of the amylase units and cell growth), both isolates produced significant amylase with the only extract of potato peels, without any other supplements. The trends further indicated that while additional complex sources, such as yeast extract and peptone can enhance the cell growth of the actinobacteria, the amylase production remained unaltered. The study projects the significance of waste raw materials for the production of enzymes in extremophilic microorganisms.

Heterologous Expression and Structural Elucidation of a Highly Thermostable Alkaline Serine Protease from Haloalkaliphilic Actinobacterium, Nocardiopsis sp. Mit-7

A highly thermostable alkaline serine protease gene (SPSPro, MN429015) obtained from haloalkaliphilic actinobacteria, Nocardiopsis sp. Mit-7 (NCIM-5746), was successfully cloned and overexpressed in Escherichia coli BL21 under the control of the T7 promoter in the pET Blue1 vector leading to a 20-kDa gene product. The molecular weight of the recombinant alkaline protease, as determined by SDS-PAGE and the Mass Spectrometer (MALDI-TOF), was 34 kDa. The structural and functional attributes of the recombinant thermostable alkaline serine protease were analyzed by Bioinformatic tools. 3D Monomeric Model and Molecular Docking established the role of the amino acid residues, aspartate, serine, and tryptophan, in the active site of thealkaline protease.The activity of the recombinant alkaline protease was optimal at 65 °C, 5 °C higher than its native protease. The recombinant protease was also active over a wide range of pH 7.0-13.0, with a maximal activity of 6050.47 U/mg at pH 9. Furthermore, the thermodynamic parameters of the immobilized recombinant alkaline protease suggested its reduced vulnerability against adverse conditions under which the enzyme has to undergo varied applications.

Development of a microbial protease for composting swine carcasses, optimization of its production and elucidation of its catalytic hydrolysis mechanism

BACKGROUND

Dead swine carcass composting is an excellent method for harmless treatment and resource utilization of swine carcass. However, poor biodegradation ability of traditional composting results in poor harmless treatment effect. Researches report that the biodegradation ability of composting can be improved by inoculation with enzyme-producing microorganisms or by inoculation with enzyme preparations. At present, the researches on improving the efficiency of dead swine carcass composting by inoculating enzyme-producing microorganisms have been reported. However, no work has been reported on the development of enzyme preparations for dead swine carcass composting.

METHODOLOGY

The protease-producing strain was isolated by casein medium, and was identified by 16 S rRNA gene sequencing. The optimal fermentation conditions for maximum protease production were gradually optimized by single factor test. The extracellular protease was purified by ammonium sulfate precipitation and Sephadex G-75 gel exclusion chromatography. The potential for composting applications of the purified protease was evaluated by characterization of its biochemical properties. And based on amino acid sequence analysis, molecular docking and inhibition test, the catalytic hydrolysis mechanism of the purified protease was elucidated.

RESULTS

In this study, a microbial protease was developed for swine carcass composting. A protease-producing strain DB1 was isolated from swine carcass compositing and identified as Serratia marcescen. Optimum fermentation conditions for maximum protease production were 5 g/L glucose, 5 g/L urea, 1.5 mmol/L Mg²⁺, initial pH-value 8, inoculation amount 5%, incubation temperature 30 °C and 60 h of fermentation time. The specific activity of purified protease reached 1982.77 U/mg, and molecular weight of the purified protease was 110 kDa. Optimum pH and temperature of the purified protease were 8 and 50 °C, respectively, and it had good stability at high temperature and in alkaline environments. The purified protease was a Ser/Glu/Asp triad serine protease which catalyzed substrate hydrolysis by Glu, Arg, Ser, Asp and Tyr active residues.

CONCLUSIONS

In general, the microbial protease developed in this study was suitable for industrial production and has the potential to enhance composting at thermophilic stage. Moreover, the catalytic hydrolysis mechanism of the protease was further analyzed in this study.

Efficiency of Microencapsulation of Proteolytic Enzymes

Currently, special attention is paid to the study of the effectiveness of the immobilization method—microencapsulation. The aim of the research is to obtain a complex enzyme preparation from pepsin and papain by sequential microencapsulation of enzymes in a pseudo-boiling layer and to evaluate its tenderizing effect on pork. The objects of research were enzymes: pepsin and papain, which were microencapsulated in a protective coating of maltodextrin. It was found that the biocatalytic activity of the complex enzyme preparation is higher than that of pure enzymes. Microencapsulation allows maintaining the high proteolytic activity of enzymes for a long storage period. It has been shown that the thickness of the protective layer during microencapsulation of pepsin and papain in the pseudo-boiling layer of maltodextrin should be in the range of 4–6 microns. During the research, the physicochemical properties of pork were studied depending on the duration of fermentation. It was found that the maximum activity of immobilized enzymes is shifted to the alkaline side. Pork salting with the use of a microencapsulated enzyme preparation in the brine increases the water-binding capacity of proteins to a greater extent in comparison with brine with pure enzymes. The presented data show the high efficiency of sequential microencapsulation of the enzyme pepsin and then papain into a protective layer of maltodextrin in order to preserve their activity during storage.