Pleurotus pulmonarius: a protease-producing white rot fungus in lignocellulosic residues

Thermothelomyces thermophilus cultivated with residues from the fruit pulp industry: enzyme immobilization on ionic supports of a crude cocktail with enhanced production of lichenase

β-Glucans comprise a group of β-D-glucose polysaccharides (glucans) that occur naturally in the cell walls of bacteria, fungi, and cereals. Its degradation is catalyzed by β-glucanases, enzymes that catalyze the breakdown of β-glucan into cello-oligosaccharides and glucose. These enzymes are classified as endo-glucanases, exo-glucanases, and glucosidases according to their mechanism of action, being the lichenases (β-1,3;1,4-glucanases, EC 3.2.1.73) one of them. Hence, we aimed to enhance lichenase production by Thermothelomyces thermophilus through the application of response surface methodology, using tamarind (Tamarindus indica) and jatoba (Hymenaea courbaril) seeds as carbon sources. The crude extract was immobilized, with a focus on improving lichenase activity, using various ionic supports, including MANAE (monoamine-N-aminoethyl), DEAE (diethylaminoethyl)-cellulose, CM (carboxymethyl)-cellulose, and PEI (polyethyleneimine)-agarose. Regarding lichenase, the optimal conditions yielding the highest activity were determined as 1.5% tamarind seeds, cultivation at 50 °C under static conditions for 72 h. Moreover, transitioning from Erlenmeyer flasks to a bioreactor proved pivotal, resulting in a 2.21-fold increase in activity. Biochemical characterization revealed an optimum temperature of 50 °C and pH of 6.5. However, sustained stability at varying pH and temperature levels was challenging, underscoring the necessity of immobilizing lichenase on ionic supports. Notably, CM-cellulose emerged as the most effective immobilization medium, exhibiting an activity of 1.01 U/g of the derivative (enzyme plus support), marking a substantial enhancement. This study marks the first lichenase immobilization on these chemical supports in existing literature.

Production of milk-coagulating protease by fungus Pleurotus djamor through solid state fermentation using wheat bran as the low-cost substrate

Proteases are enzymes that hydrolyze peptide bonds present in proteins and peptides. They are widely used for various industrial applications, such as in the detergent, food, and dairy industries. Cheese is one of the most important products of the dairy industry, and the coagulation stage is crucial during the cheese-making process. Enzymatic coagulation is the most common technique utilized for this purpose. Microbial enzymes are frequently used for coagulation due to their advantages in terms of availability, sustainability, quality control, product variety, and compliance with dietary and cultural/religious requirements. In the present study, we identified and subsequently characterized milk coagulant activity from the fungus Pleurotus djamor PLO13, obtained during a solid-state fermentation process, using the agro-industrial residue, wheat bran, as the fermentation medium. Maximum enzyme production and caseinolytic activity occurred 120 h after cultivation. When the enzyme activity against various protease-specific synthetic substrates and inhibitors was analyzed, the enzyme was found to be a serine protease, similar to elastase 2. This elastase-2-like serine protease was able to coagulate pasteurized whole and reconstituted skim milk highly efficiently in the presence and absence of calcium, even at room temperature. The coagulation process was influenced by factors such as temperature, time, and calcium concentration. We demonstrate here, for the first time, an elastase-2-like enzyme in a microorganism and its potential application in the food industry for cheese production.

Comparison of Trichoderma longibrachiatum Xyloglucanase Production Using Tamarind (Tamarindus indica) and Jatoba (Hymenaea courbaril) Seeds: Factorial Design and Immobilization on Ionic Supports

Xyloglucan (XG) is the predominant hemicellulose in the primary cell wall of superior plants. It has a fundamental role in controlling the stretching and expansion of the plant cell wall. There are five types of enzymes known to cleave the linear chain of xyloglucan, and the most well-known is xyloglucanase (XEG). The immobilization process can be used to solve problems related to stability, besides the economic benefits brought by the possibility of its repeated use and recovery. Therefore, this study aims at the optimization of the xyloglucanase production of Trichoderma longibrachiatum using a central composite rotatable design (CCRD) with tamarind and jatoba seeds as carbon sources, as well as XEG immobilization on ionic supports, such as MANAE (monoamine-N-aminoethyl), DEAE (diethylaminoethyl)-cellulose, CM (carboxymethyl)-cellulose, and PEI (polyethyleneimine). High concentrations of carbon sources (1.705%), at a temperature of 30 °C and under agitation for 72 h, were the most favorable conditions for the XEG activity from T. longibrachiatum with respect to both carbon sources. However, the tamarind seeds showed 23.5% higher activity compared to the jatoba seeds. Therefore, this carbon source was chosen to continue the experiments. The scaling up from Erlenmeyer flasks to the bioreactor increased the XEG activity 1.27-fold (1.040 ± 0.088 U/mL). Regarding the biochemical characterization of the crude extract, the optimal temperature range was 50–55 °C, and the optimal pH was 5.0. Regarding the stabilities with respect to pH and temperature, XEG was not stable for prolonged periods, which was crucial to immobilizing it on ionic resins. XEG showed the best immobilization efficiency on CM-cellulose and DEAE-cellulose, with activities of 1.16 and 0.89 U/g of the derivative (enzyme plus support), respectively. This study describes, for the first time in the literature, the immobilization of a fungal xyloglucanase using these supports.