Enhanced Green Production of Biobutanol by Novel Fusants of Two and Three Clostridia

Banafsheh Mohtasebi

doi:10.32920/ryerson.14661153

Abstract

Protoplast fusion, which is a novel genetic engineering approach, was developed between mesophilic and thermophilic butanol producing bacteria to enhance production of biobutanol as a green energy resource. Three strains of anaerobic gram-positive clostridia were fused through a protoplast fusion technique to produce biobutanol from wheat straw as a feedstock during the process of Simultaneous Saccharification and Fermentation (SSF). These strains have the natural enzymatic ability for biobutanol production, and include Clostridium beijerinckii (ATCC BA101), Clostridium thermocellum, and Thermoanaerobacterium saccharolyticum. The objective of the present study was to increase enzymatic activity during saccharification by raising the temperature of fermentation to increase biobutanol production. Results showed that protoplast fusion of thermophilic and mesophilic clostridia have led to improving thermostability in a fermentation medium at 45°C. This represents the optimum temperature for enzymatic hydrolysis. Results also showed that the fused strain produced essential hydrolysis enzymes, which eliminated the need to add any enzymes during the hydrolysis step. Furthermore, results in the present study demonstrated that the fused culture of bacteria was able to tolerate the elevated concentration of acetone, butanol, and ethanol during production, which resulted in higher biobutanol production of 13.8 g/L. This study included a comparison to the coculture as a benchmark to account for the effects of protoplast fusion.

Highlights

The growing consumption of fossil fuels has been one of the main sources of greenhouse gas emissions that lead to undesirable damage to air quality
Protoplast Formation and Cell Wall Regeneration of Wild Strains In order to compare the regeneration of the cell wall of each bacterial strain, protoplasts were diluted in PPM and plated at various concentrations on regeneration medium
It should be noted that the presence of the biomarker control genes in all growth cycles confirms the existence of genes from both wild strains in the fused strains

Summary

Introduction

The growing consumption of fossil fuels has been one of the main sources of greenhouse gas emissions that lead to undesirable damage to air quality. High prices of oil coupled with instability of barrel supplies have initiated a considerable interest in alternative and renewable energy sources. The first generation of biofuels was made from edible sources such as wheat, corn, and sugars by the action of microorganisms. This generation was not successful, since it threatened traditional food supplies as well as biodiversity. The second generation of biofuels, derived from lignocellulosic crops, has achieved a lot of attention, because it is produced from residual non-food crops or agricultural residues which are sustainable resources. The third generation of biofuel that is made from algae, has attracted lots of attentions due to its ability to be cultured on unsuitable lands for agriculture (Hartman, 2008)

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Results

Conclusion