Optimal protease production condition for Prevotella ruminicola 23 and characterization of its extracellular crude protease

Effect of nutmeg essential oil (Myristica fragrans Houtt.) on methane production, rumen fermentation, and nutrient digestibility in vitro

The study evaluated the effect of adding of nutmeg (Myristica fragrans Houtt.) essential oil (NEO) as a feed additive on methane production, rumen fermentation parameters, rumen enzyme activity, and nutrient digestibility in vitro. This study was divided into three treatments based on the level of NEO addition, which included 0 µL/L (T0), 100 µL/L (T1), and 200 µL/L (T2). The feed substrate composition consisted of king grass as forage and concentrate in a 60:40 ratio. Feed fermentation was conducted using the Menke and Steingass gas production and two-step Tilley and Terry in-vitro digestibility technique. The data obtained from the study were analyzed using one-way ANOVA and if there were differences between means, they were further assessed using DMRT. The results showed that T2 treatment significantly decreased (P < 0.05) ammonia (NH3) levels, total VFA, acetate, propionate, butyrate, and microbial protein (P < 0.05). Methane production and the activity of rumen protease enzyme significantly decreased (P < 0.05) at T1 and T2 treatment. The T2 treatment significantly reduced (P < 0.05) protein digestibility (IVCPD) at 48 h, while IVCPD at 96 h significantly increased (P < 0.05). On the other hand, the addition of nutmeg essential oil did not effect the activity of the amylase, carboxymethyl cellulase, and β-glucosidase enzymes, as well as the in-vitro digestibility of dry matter (IVDMD), crude fiber (IVCFD), and organic matter (IVOMD). The conclusion drawn from this study is that the optimum level for NEO is 200 µL/L, which can reduce methane production and increase crude protein digestibility at 96 h without any negative effect on rumen fermentation and nutrient digestibility.

Shifts in enzymatic activities and microbial community structures in the bioenhanced treatment of ship domestic sewage under microaerobic conditions

A bioenhancement strategy for improving the anaerobic degradation efficiency of ship domestic sewage under microaerobic conditions was proposed in this study. Strains Stenotrophomonas sp. MSPP05 and Prevotella sp. MSPP07 with high organic-degrading efficiency and extracellular hydrolase yield were used for the bioenhancement of activated sludge. In batch experiments, the removal rates of chemical oxygen demand and total nitrogen reached 94.5% and 66.9% after 72 h of degradation. The activities of dehydrogenase, extracellular amylase, and protease in the treatment group were 1.2, 1.4, and 2.0 times higher than those in the control group. Microbial community analysis showed that exogenous enhanced strains competed with original microorganisms and became dominant. One-stage continuous stirred tank reactor with bioenhanced activated sludge ran steadily for 90 days with average effluent COD and TN concentrations of 87.5 and 14.6 mg/L. The feasibility of improving organic-degrading efficiency through bioenhancement by using exogenous hydrolase-producing strains was confirmed under microaerobic conditions. This work provided a theoretical basis for improving treatment effects and developing a new technique for ship domestic sewage treatment.

Production of Alkaline Proteases using Aspergillus sp. Isolated from Injera: RSM-GA Based Process Optimization and Enzyme Kinetics Aspect

Alkaline proteases are well known to be significant industrial enzymes. This study focused on isolating the fungus producing proteases from, a typical Ethiopian food, Injera. Further, the process optimization for protease production using response surface methodology (RSM) and the characterization of the acquired protease were investigated. The 18S rDNA gene sequence homology of the fungus isolate revealed that it was Aspergillus sp. Further, it was deposited in NCBI GenBank with accession number MK4262821. Using the isolate, owing to maximize the protease production, the independent process parameters, temperature, pH, and sucrose concentration were optimized using RSM followed by a genetic algorithm (GA). Based on the statistical approach by RSM-GA optimization, maximum enzyme activity (166.4221 U/ml) was found at 30.5 °C, pH 8.24, and 0.316% sucrose concentration. Also, the crude cocktail of enzymes acquired from optimal condition was partially purified using ammonium which showed that the increased activity by 1.96-fold. Considerably, the partially purified enzyme exhibited stable performance during the temperature range 30-60 °C, pH range 7-10, and NaCl concentration of 0.5-2 mM. Also, the antioxidant activity, degree hydrolysis for the protein, Michaelis-Menten (M-M) kinetic parameters, and activation energy were determined for the obtained enzyme cocktail. It showed that the M-M kinetic parameters, Km (5.54 mg/ml), and Vmax (24.44 mg/ml min) values were observed. Using Arrhenius law, the value of activation energy for the enzyme cocktail was determined as 32.42 kJ/mol.

Optimization of Nutrients and Culture Conditions for Alkaline Protease Production Using Two Endophytic Micrococci: Micrococcus aloeverae and Micrococcus yunnanensis

An endophytic species of Micrococcus was isolated from Aloe vera leaf (syn. Aloe barbadensis) and screened for protease production with five other species of Micrococcus. Data indicated that endophytic Micrococcus aloeverae AE-6 MCC 2184^T and Micrococcus yunnanensis DSM 21948^T showed efficient protease production potential and secreted active protease at high salt (10%), temperature (40 °C) and in wide range of pH 8-10. Unlike M. yunnanensis DSM 21948^T, protease production by M. aloeverae AE-6 MCC 2184^T was stringently controlled by pH. Protease induction study using different group of peptides, peptide carbohydrates and peptide macronutrient combinations showed variable response with both the organisms. Result indicated that the amount of protease was not directly related to cell biomass but it depends on nature of inducible peptides. In this study we also developed a modified agar-well assay for semi-quantitative data from large number of replicates.