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.
