Feasibility of exhausted sugar beet pulp as raw material for lactic acid production

Abstract

Exhausted sugar beet pulp pellets (ESBPP), a sugar industry by-product generated after sugar extraction in the sugar production process, have been used as a raw material for lactic acid (LA) production via hydrolysis and fermentation by Lactobacillus casei. The present study proposes simultaneous saccharification and fermentation (SSF) of ESBPP to design a more cost-effective process. The effects of pH control, nutrient supplementation and solid addition in fed-batch SSF on lactic acid production were investigated.

RESULTS The highest LA concentration (26.88 g L–1) was reached in fed-batch SSF at a solid/liquid loading of 0.2 g mL–1, with pH control (by adding 30 g L–1 CaCO3 to the medium) and nutrient supplementation (by adding 20 mL of MRS medium per 100 mL of buffer). Under these conditions, a maximum productivity of 0.63 g L−1 h−1 was achieved, 2.7 times higher than that of the control experiment (SSF inoculated at time 0 h). However, a slightly lower LA yield was obtained, revealing the need for an increasing dose of enzymes at high solid-loading SSF.

CONCLUSION An efficient fed-batch SSF strategy with pH control and MRS supplementation is described in the present study, attaining higher LA productivity compared to separate hydrolysis and fermentation and SSF.