High-titer lactic acid production from pilot-scale pretreated non-detoxified rice straw hydrolysate at high-solid loading

Abstract

Lignocellulosic biomasses are promising feedstocks for the production of high-value chemicals because they are abundant, inexpensive, renewable, sustainable, environmentally friendly, and can potentially reduce pollution. Furthermore, lignocellulose biomass is non-edible and a source of fermentable sugars, which makes it ideal for the fermentation of various biochemicals, such as bio-based lactic acid (LA). Furthermore, it contributes to the economic sustainability of biorefineries. LA is an industrially significant product with a large and rapidly growing market due to its attractive features and benefits. The current study demonstrates high-titer lactic acid (LA) fermentation from pretreated rice straw using co-fermenting (C5 & C6 sugars) Lactobacillus lactis 2369. Rice straw (RS) was chemically pretreated with mild acid additive in a pilot-scale (250 Kg day–1) steam-explosion unit. At first, the crude dilute acid pretreated slurry was enzymatically hydrolyzed using commercial cellulases (1.5–10 FPUg−1 residue) at 50 °C for 48 h followed by LA production for 96–140 h. In the current study high titer, LA production (82.2 gL−1) as well as higher conversion yield (87.2%) with the productivity of 0.61 gL−1h−1 were obtained with high substrate solid loading (20% wv−1) and low enzyme dose (5 FPU g−1) at 42 °C.