Optimization of growth temperature for the production of cellulase in Myceliophthora thermophila

Myceliophthora thermophila can produce various cellulolytic enzymes that degrade the major polysaccharides of plant biomass. Cellulase (exoglucanase) is an enzyme produced by these cells and excreted in the supernatant of the culture broth during fermentation processes. Different temperatures were investigated as a means to increase production yield of the cellulase activity during seven days of fermentation. The highest yield was observed for the temperature range of 45-48 ˚C. The highest enzyme activity was 24.3 ± 0.2 U/mL of supernatant, which was observed during the culture growth at 45 ˚C. The enzyme activity decreased slightly at 48 ˚C to 21.5 ± 0.2 U/mL of supernatant. At 32 ˚C, 38 ˚C, and 41 ˚C, the enzyme activity decreased by nearly 50% (12.4-13.1 U/mL) in comparison to yields at 45 ˚C and 48 ˚C. For these measurements, one unit of enzyme activity is defined as the amount of enzyme releasing 1 μmol of p-nitrophenol per minute at pH 5.0 and 50 ˚C. In addition, the uncommon buff color of culture and branched hyphal cells were observed in 45 ˚C and 48 ˚C fermentation flasks.