Solid-state fermentation for l-lactic acid production from agro wastes using Lactobacillus delbrueckii

Abstract

A viable process based on a low cost production media is desired to enhance the economics of fermentative production of l-lactic acid. Attempts were made to exploit two agro-industrial wastes, cassava bagasse and sugarcane bagasse, as a raw material and inert solid support using solid-state fermentation (SSF). Gelatinised cassava bagasse was enzymatically hydrolysed and starch hydrolysate containing reducing sugar was used to moisten the inert sugarcane bagasse, which was used as the solid support for SSF. This substrate was supplemented with 0.5 g/5 g support NH 4Cl and yeast extract. SSF was carried out in 250 ml Erlenmeyer flasks at 37 °C using Lactobacillus delbrueckii as inoculum. Key parameters such as initial moisture content and initial sugar were optimised statistically by response surface methodology. A maximum of 249 mg/gds l-lactic acid was obtained after 5 days of fermentation under the optimised conditions with a conversion efficiency of about 99% of the initial reducing sugars.