Evaluation of different fungi and bacteria strains for production of cellulases by submerged fermentation using sugarcane bagasse as carbon source: Effect of substrate concentration and cultivation temperature

Abstract

Cellulases (enzymes of great potential in biotechnology) are currently of interest due to their applicability in the hydrolysis of cellulose from lignocellulosic materials, producing fermentable sugars for alcohol production. The great demand for efficient enzymes is the driving force to prospect new cellulases-producing microorganisms, as well as to optimize the enzyme production step. Many variables can be optimized in microorganism cultivation, such as pH, type of microorganism, induction, temperature, type and concentration of substrate, among others. This work aimed to evaluate the production of cellulases by submerged fermentation from three strains of filamentous fungi (Trichoderma koningii, Penicillium species, Rhizomucor species) and two strains of bacteria (Bacillus megaterium and Bacillus subtilis), using sugarcane bagasse as substrate. Variations in substrate concentrations (0.5, 1.6 and 2.7%, w/v) and temperature (28, 33 and 38°C) were evaluated on volumetric activity. The best fungus was T. koningii (3130.4 IU/L) using 2.7% natural sugarcane bagasse at 28°C.  Among the bacteria, B. megaterium stood out with an enzyme production in range of 130 to 156.7 IU/L (at 28-33°C using natural and acid-alkaline pretreated bagasses), although up to around 20 times lower than the production by the T. Koningii.   Key words: Microorganisms, lignocellulosic biomass, cellulolytic enzymes, pretreated biomass.