Growth kinetics of Bacillus subtilis (Bal3) for production of cellulolytic crudes used in the bioethanol production industry

Abstract

Biotechnologically manageable microbiota that can produce enzyme complexes of interest is a thriving research field. After careful collection and laboratory culture, the microorganisms can develop hydrolysis and fermentation processes in bioreactors. Kinetic models for their growth are applied, being the most used those of Monod, Moser, Blackman and Powell, which combine mathematical models and experimental work. The objective of this study was to determine the kinetic behavior of Bacillus subtilis (Bal3) to size the equipment needed to obtain enough amount of enzimes to produce  500 hl of ethanol at 70% per day. A medium composed of 60 g of sugarcane bagasse and 350 ml of whey in 1L of water with 0.02 g of inoculum was placed in a 2L Bioflo/CelliGen 115 bioreactor for 130 h at 20° C and 150 rpm. The pH ranged from 6.8 (start) to 5.8 (end). A biomass-substrate yield of 19.34% and a biomass productivity of 0.048 g/L per hour were obtained. With the kinetic models of Velhurs-Pearl, Pirt and Luedeking-Piret, the mass balance was performed and the equipment volume was calculated. Monod's model was considered to adequately represent the growth behavior of the bacteria.