Isolation, Characterization and Kinetic Modeling of Carboxymethyl Cellulose Degrading Ethanologenic Bacterial Strains

Abstract

Ethanol has become a major target as an alternate fuel in the wake of a fossil fuel crisis. Cellulose provides a cheap biomass for the production of ethanol. In the present study, bacterial strains were isolated from different environmental sources and screened for their cellulolytic activity upon Carboxymethyl Cellulose (CMC). Ethanol production by the bacterial isolates was tested using the potassium dichromate test and subsequently confirmed through High Performance Liquid Chromatography. Two of the bacterial isolates were identified as Lactococcus lactis (HI-W) and Lactobacillus pentosus (HI-Lb2), which showed highest cellulose degrading activity at 0.5% CMC concentration, temperature 37ºC, pH 6.0, under oxygen limiting conditions, producing a reducing sugar concentration of 2.3mg/ml and 2.1mg/ml respectively and an ethanol concentration of 1.764mg/ml and 1.684mg/ml respectively in batch fermentation. A third unidentified bacterial strain produced 1.8mg/m of reducing sugars and 1.544mg/ml ethanol at 37ºC and pH 7.0 under the same conditions. Furthermore the reducing sugar and ethanol production by the strains was modeled through Hybrid Petri Nets using kinetic data obtained in the wet lab. The computational model results showed good correlation with the wet lab results with respect to reducing sugar concentration and ethanol production. The current study can be can be taken forward through a better understanding of media requirements and using advanced molecular techniques such as metabolic and enzyme engineering for enhancing ethanol production with the help of improvements in the kinetic model.