Lactic acid production by Lactobacillus coryniformis employing lignocellulosic biomass

During the past decades, considerable efforts have been made to utilize agricultural and forest residues as biomass feedstock for the production of bioethanol as an alternative fuel. Sugarcane bagasse, composed of 38.1 w% cellulose, 28.4 w% hemicellulose and 18.4 w% lignin, represents the main lignocellulosic material to be considered by most of tropical countries. The lactic acid is a naturally occurring organic acid, with added value and versatile considering numerous applications in the food industry (which holds about 85% of demand), pharmaceutical, chemical, textile and leather. Thus, the aim of this study was to evaluate the fermentation utilizing strains of Lactobacillus coryniformis by simultaneous saccharification and fermentation (SSF) process. Initially, to make easier the accessibility of cellulases to the cellulose microfibrils, the bagasse had to be submitted to a pretreatment with diluted acid to fractionate it and extract the hemicellulose component from the solid residue termed cellulignin. This solid residue was pretreated using NaOH (4%) aiming at its partial delignification. Thereafter, the pretreated cellulignin underwent the action of a commercial celulolytic preparation, allowing the conversion of cellulose to glucose. This enzymatic pretreatment occurred under temperature of 50°C for 12 hours, after which the temperature was reduced to 37°C and the system was inoculated with cells of L. coryniformis.  The Lactobacillus strain reached 20 g/L of lactic acid, employing 10% of the initial inoculum and orbital agitation of 120 rpm. The results were very interesting and pointed out for future developments.