Milk-clotting enzymes produced byAspergillus flavo furcatisstrains on Amazonic fruit waste

Production, properties and some applications of protease from alkaliphilic Bacillus sp. EBTA6

Extracellular protease production by a novel strain, Bacillus sp. EBTA6, has been optimized by using central composite design of response surface methodology and properties and industrial applications of crude enzyme have been investigated. Three independent variables (temperature, pH and yeast extract concentration) chosen in the experimental design were significant terms and reduced cubic model fit with the design at p < 0.0001 level. The recommended temperature, pH and yeast extract concentration were 30 °C, 8, and 15 g/L, respectively. Crude enzyme displayed activity over a wide pH and temperature ranges having the optimum at 50-60 °C and pH 8. It was quite stable at high pH values and at 50 °C. Amongst the metal ions (Mg⁺, Cu²⁺, Ca²⁺, Zn²⁺, K²⁺, and Sn²⁺), Ca²⁺ enhanced the activity and the others either decreased or did not change it. The enzyme activity was reduced by phenyl-methyl-sulfonyl fluoride (PMSF), and ethylene diamine tetra acetic acid (EDTA). The results revealed that the protease was serine alkaline type. Tween 20 and Tween 80 did not inhibit the enzyme, however, sodium dodecyl sulfate (SDS), reduced it by 39%. It completely removed blood stain in 20 min and coagulated milk in the presence of CaCl₂.

Optimization of media composition and growth conditions for production of milk-clotting protease (MCP) from Aspergillus oryzae DRDFS13 under solid-state fermentation

This study reports the optimization of milk-clotting protease production from Aspergillus oryzae DRDFS13 under solid-state fermentation (SSF) in both one-variable-at-a-time and response surface methodology (RSM). The production and optimization of milk-clotting protease obtained from Aspergillus oryzae DRDFS13 under solid-state fermentation (SSF) using different agro-industrial wastes as solid substrates were studied. The agro-industrial wastes used included wheat bran, rice bran, pea bran, and grass pea bran. The chemical composition of the best solid substrate was tested using standard methods. Others cultivation parameters were studied, and the results showed that the optimum fermentation medium composed of wheat bran, casein (1% w/w), and glucose (0.5% w/w) and the conditions for maximum milk-clotting protease production were at the moisture content of 55.0%, inoculum of 0.5*10⁶ spores/mL, incubation temperature of 30 °C, pH of 6.0, and fermentation time of 5 days. The highest milk-clotting activity was obtained from the crude enzyme extracted using 0.1 M NaCl and partial purification of the crude enzyme using chilled acetone, and 80% (NH₄)₂SO₄ increased the ratio of MCA/PA from 0.56 to 1.30 and 0.65, respectively. Moreover, the highest MCA (137.58 U/mL) was obtained at a casein concentration of 0.5%, pH 4.0, and 25 °C, using RSM. Thus, results from the present study showed that the optimization of milk-clotting protease production from A. oryzae DRDFS 13 under SSF by both one-variable-at-a-time and RSM significantly increased the milk-clotting activity. This is the first report from a fungus in the Ethiopian setting and a modest contribution to highlight the potential of harnessing microbial protease enzymes for industrial applications.

Newly Effective Milk-Clotting Enzyme from Bacillus subtilis and Its Application in Cheese Making

A new effective milk-clotting enzyme (BY-1) was produced from Bacillus subtilis PNG27. The analysis of MALDI-TOF-MS/MS showed that it belongs to the peptidase M4 family and had 521 amino acids. It had a higher proteolytic activity on α-casein, β-casein, κ-casein, and β-lactoglobulin than Rennet. Besides, BY-1 could decrease the curd time of poor-curd, UHT, refrigerated, and reconstituted milk. Moreover, two kinds of cheese were, respectively, made by BY-1 and Rennet. The results showed that the protein hydrolysates (WSN, CTA-N, and PTA-N) of cheese made by BY-1 were higher than that of Rennet. Flavor compounds (28) were detected from the cheese made by BY-1, whereas 15 compounds were detected from Rennet. The sensory evaluation indicated that the cheese produced by BY-1 exhibited better flavor and overall acceptability. Therefore, BY-1 could be widely used in cheese production.

Production of mycelial biomass by the Amazonian edible mushroom Pleurotus albidus

Edible mushroom species are considered as an adequate source of food in a healthy diet due to high content of protein, fiber, vitamins, and a variety of minerals. The representatives of Pleurotus genus are characterized by distinct gastronomic, nutritional, and medicinal properties among the edible mushrooms commercialized worldwide. In the present study, the growth of mycelial biomass of Pleurotus albidus cultivated in submerged fermentation was evaluated. Saccharose, fructose, and maltose were the three main carbon sources for mycelial biomass formation with corresponding yields of 7.28 g L⁻¹, 7.07 g L⁻¹, and 6.99 g L⁻¹. Inorganic nitrogen sources did not stimulate growth and the optimal yield was significantly higher with yeast extract (7.98 g L⁻¹). The factorial design used to evaluate the influence of saccharose and yeast extract concentration, agitation speed, and initial pH indicated that all variables significantly influenced the production of biomass, especially the concentration of saccharose. The greater amount of saccharose resulted in the production of significantly more biomass. The highest mycelial biomass production (9.81 g L⁻¹) was reached in the medium formulated with 30.0 g L⁻¹ saccharose, 2.5 g L⁻¹ yeast extract, pH 7.0, and a speed of agitation at 180 rpm. Furthermore, P. albidus manifested different aspects of morphology and physiology under the growth conditions employed. Media composition affected mycelial biomass production indicating that the diversification of carbon sources promoted its improvement and can be used as food or supplement.