Objectives. Identification of cellulolytic microorganisms is of great interest to the hydrolysis of cellulosic biomass. This study focuses on the identification of cellulolytic yeasts and the optimization of cellulase activities produced by the best performing isolate. Results. 30 cellulolytic yeast isolates were selected. Enzymes produced by an isolate from the Trichosporon genus showed the property to hydrolyze different substrates: carboxymethyl cellulose (CMC), cellulose fiber, and filter paper (FP). The optimum measured temperature was 55°C for CMCase and 60°C for FPase. The optimal pH was 5 for CMCase and 4 to 6 for FPase. The effect of the substrates concentration showed that the best activities were obtained at 100 mg/mL CMC or FP. The highest activities were 0.52 for the CMCase and 0.56 for the cellulase fiber at 10 min incubation, 0.44 IU/mL at 15 min incubation, and 24 h FPase preincubation. Conclusion. Cellulases produced by the studied yeast are capable of hydrolyzing soluble and insoluble substrates at elevated temperatures and at a wide pH range. They are considerable interest in the production of fermentable sugars from lignocellulosic substrates.
In this study, thirty yeast strains isolated from the gut of coprophagous “Gymnopleurus sturmi” and twenty-four from the dung of ruminants were shown to be producers of cellulases. Cellulolytic yeast isolates could also produce other hydrolytic enzymes such as pectinase, lipase, β-glucosidase, catalase, inulinase, urease, gelatinase, and protease. The oroduction of amylase was present in only one isolate of dung of ruminants. On the other hand, the production of tannase was absent in these isolates. All the yeasts isolated from two sources could utilize various carbon sources, including sorbitol, sucrose, and raffinose, and withstand high concentrations of glucose (300 g/L), salt (100 g/L), and exogenous ethanol. They could grow in a wide pH range of 3 to 11. The growth was stable up to a temperature of 40 °C for isolates from the gut of coprophage and 37 °C for the yeast from the dung of ruminants. These activities and growing conditions were similar to the diet of coprophagous insects and the composition of ruminant manure, likely because the adaptation and distribution of these microorganisms depend on the phenology and trophic preferences of these insects.
Bacterial resistance to antibiotics and disinfectants has become a real concern. The hospital presents a favorable environment for the colonization and development of bacteria resistant to antibiotics and disinfectants. The search for new antimicrobial compounds is essential to combat this phenomenon. Tetrazole derivatives may represent a solution due to their interesting antibacterial activity. In this work, two tetrazole derivatives; thiophene-2-carbaldehyde (T2C) and 5-(thiophen-2-yl)-1H-tetrazole (5TPh-1HT), were evaluated for their antibacterial activities against a set of reference strains and strains isolated from the hospital environment. The antibacterial effect was studied by the disc diffusion method and by determination of MIC and MBC. The 5-(thiophen-2-yl)-1H-tetrazole (5TPh-1HT) has a broader spectrum of activity than its oxime derivative (T2C). The latter has bactericidal activity only on gram-negative Escherichia coli, Pseudomonas aeruginosa with MICs ranging from 0.62 mg/ml to 2.5 mg/ml, while 5TPh-1HT has a bactericidal effect on all strains with MICs ranging from 0.62 mg/ml to 1.25 mg/ml. Both products have a significant inhibitory activity on the strains tested in particular E. coli H, S. aureus H, P. aeruginosa and Streptococcus spp A. It was found that these activities vary depending on the microbial strain tested and the product applied.
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