Optimization of immobilized Lactobacillus pentosus cell fermentation for lactic acid production

Jianfei Wang,Jiaqi Huang,Shaoming Jiang,Shijie Liu,Yuchen Ning,Hannah Laffend,Jing Zhang,Mudannan Fang

doi:10.1186/s40643-020-00305-x

Abstract

Parametric optimization is an effective way in fermentation process to improve product yield and productivity in order to save time, space and financial resources. In this study, Box–Behnken design was applied to optimize the conditions for lactic acid production by immobilized Lactobacillus pentosus ATCC 8041 cell fermentation. Two quadratic models and response surface methodology were performed to illustrate the effect of each parameters and their interactions on the lactic acid yield and glucose consumption rate in immobilized L. pentosus ATCC 8041 cell fermentation. The maximum lactic acid yield was obtained as 0.938 ± 0.003 g/g glucose with a productivity of 2.213 ± 0.008 g/(L × h) under the optimized conditions of 2.0 mm bead diameter, 5.60 pH, 115.3 g/L initial glucose concentration, and 398.2 mg biomass (CDW) in 100 mL hydrogel. The analysis of variance indicated that the quadratic model was significant and could be used to scale up the fermentation process.

Highlights

Lactic acid (LA) is a hygroscopic non-toxic organic compound that has been widely utilized in the cosmetic, pharmaceutical, food, and chemical industries (Vijayakumar et al 2008)
They found that an initial glucose concentration of 9.7% to 13.3% had non-significant limitation to the LA production, but an initial glucose concentration of 18.6% or higher would lead to a significant restriction on LA production
The immobilized L. pentosus cells perform with a high fermentation efficiency and excellent stability in homofermentation for LA production

Summary

Introduction

Lactic acid (LA) is a hygroscopic non-toxic organic compound that has been widely utilized in the cosmetic, pharmaceutical, food, and chemical industries (Vijayakumar et al 2008). Chemical synthesis and fermentation are the main methods of industrial production of LA The racemic mixture (DL-LA) will be formed during LA production process by chemical synthesis method, resulting in an increase in its cost of separation and purification. Its metabolic pathway changes from homologous fermentation to heterologous fermentation, which produces LA via phosphoketolase (PK) pathway (Martinez et al 2013) Both pathways are shown as following equations: C6 H12 O6 + 2ADP + 2Pi → 2C3 H6 O3 + 2ATP (1). The aerobic fermentation of immobilized L. pentosus cells utilizing glucose is still homologous fermentation with no ethanol production, which has been confirmed based on NMR spectroscopy in our previous research. Box–Behnken design was used to optimize the bead diameter, pH, initial glucose concentration, and the weight of biomass for immobilized L. pentosus ATCC 8041 cell fermentation. The effects of these parameters on the efficiency of immobilized L. pentosus ATCC 8041 cell fermentation were discussed based on the response surface and regression model

Materials and methods

Design of experiment

Results and discussion

Findings

Conclusion