Time-course Cellulase Production by B2S8 Bacterial Isolate and Its Utilization in Bioethanol Fermentation from Corn Stover

Abstract

Cellulase enzymes play crucial roles in hydrolyzing cellulose into simple sugars, which potentially serve as substrates for bioethanol production. These enzymes can be sourced from cellulolytic bacteria, which are characterized by exhibiting different growth and enzyme production patterns. This study was aimed to determine the cellulase activity of B2S8 bacteria previously isolated from compost products, followed byoptimization oftheir application for bioethanol fermentation. The research was conducted in two stages: examination of the effect of incubation time on bacterial growth and enzymatic activity within 144 h divided into 19 levels, and the second stage was to optimize fermentation conditions using a factorial randomized block design with two factors: crude cellulase enzyme concentration (7, 9, and 11% v/v) and fermentation temperature (30, 35, and 40 °C). The results of the first stage showed that incubation time significantly influenced the optical density of bacterial culture measured at 660 nm (OD660), pH, and enzyme activity. The highest enzyme production was observed at 72 h, with OD660 2.4, pH 7, endoglucanase activity 0.097 IU/mL, exoglucanase activity 0.018 IU/mL, soluble protein 0.0363 mg/mL, and specific activities of 2.906 IU/mg and 0.018 IU/mg of endoglucanase and exoglucanase, respectively. The following optimization study revealed that the combination of 9% (v/v) enzyme concentration and fermentation at 35 °C yielded the highest ethanol content (0.50 ± 0.07% v/v), with a resulting pH of 4.85 ± 0.07, total soluble solids of 3.4 ± 0.07 °Brix, and reducing sugars value of 0.802 ± 0.03 °Brix. In this work, isolate B2S8 demonstrated promising cellulase production and effective application in bioethanol fermentation, which indicates its potential for further development in bioconversion processes.