Bioethanol Production from Sugarcane Molasses by Engineered Strain Lactobacillus Casei E1

Abstract Sugarcane molasses are considered a potential source for bioethanol's commercial production because of its availability and low market price. It contains high concentrations of fermentable sugars that can be directly metabolized by microbial Fermentation. Lactic acid bacteria, especially Lactobacillus casei, have a high potential to be a biocatalyst in ethanol production that they are characterized by strong abilities of carbohydrate metabolism, ethanol synthesis, and high alcohol tolerance. This study aimed to evaluate the feasibility of producing ethanol from sugarcane molasses by Lactobacillus casei used engineering strain L. casei E1 as a starter culture. The effects of environmental factors on the metabolism of L. casei E1 were analyzed by high-performance liquid chromatography (HPLC) system, and the gene expression of key enzymes in carbon source metabolism was detected using quantitative real-time PCR (RT-qPCR). Results showed that the strain could grow well, ferment sugar quickly and produce high yielded ethanol in cane molasses. By fermenting this bacterium anaerobically at 37°C for 36 h incubation in 5 °BX molasses when the fermenter's pH was controlled at 6.0, ethanol yield reached 13.77 g/L, and carbohydrate utilization percentage was 78.60%. RT-qPCR results verified the strain preferentially ferment glucose and fructose of molasses to ethanol at the molecular level. In addition, the metabolism of sugars, especially fructose, would be inhibited by elevating acidity. Our findings support the theoretical basis for exploring Lactic acid bacteria as a starter culture for converting sugarcane molasses into ethanol.