Polyurethane foam as an inert carrier for the production of L(+)-lactic acid by Lactobacillus casei under solid-state fermentation

Abstract

Production of L-lactic acid in solid-state fermentation (SSF) using polyurethane foam (PUF) as inert support moistened with cassava bagasse starch hydrolysate. PUF impregnated with cassava bagasse starch hydrolysate as major carbon source was used for the production of L-lactic acid using Lactobacillus casei in solid-state condition. The key parameters such as reducing sugar, inoculum size and nutrient mixture were optimized by statistical approach using response surface methodology. More than 95% conversion of sugars to lactic acid from 4 g reducing sugar per gram dry support was attained after 72 h when the inert substrate was moistened with 6.5 ml of nutrient solution and inoculated with 1.5 x 10(9) CFU of L. casei. While considering the lactate yield based on the solid support used, a very high yield of 3.88 g lactic acid per gram PUF was achieved. PUF acted as an excellent inert support for L. casei and provided a platform for the utilization of starchy waste hydrolysate in a lower reactor volume. This is a cost effective cultivation of lactic acid bacteria for producing lactic acid from agro based waste products such as cassava bagasse. This is the first report on the exploitation of PUF as an inert support for lactate production under SSF.