2.5.3 Microbiological Production of Bioethanol
Enzymatic hydrolysis is a preferred procedure where cellulose is hydrolysed into
fermentable sugars and it can be catalysed by cellulase enzymes. Production of
cellulase enzymes can be done by bacteria (Clostridium, Bacillus,
Thermomonospora, Bacteriodes, Streptomyces, etc.) and fungi (Sclerotium rolfsii,
Phanerochaete chrysosporium and species of Trichoderma, Aspergillus, Penicillium). Several aspects like porosity, cellulose fibre crystallinity, lignin (which is not
fermentable) and hemicellulose content, etc. affect the hydrolysis of cellulose. Thus,
hydrolysis can be improved by reducing the cellulose crystallinity and removing
lignin and hemicellulose with an increase in porosity during the pretreatment
process.
The application of agricultural wastes or residues and bagasse (a by-product of
sugar industry) to produce bioethanol has been shown in recent studies. The major
drawback was the cost of cellulase enzymes used in the saccharification process, and
ultimately leads to increased production cost. To achieve high product yield and
reducing production cost, a lot of research has been conducted where enzyme
Fig. 2.3 Production of bioethanol from lignocellulosic biomass (adapted from Lin and Tanaka
2006; Balat et al. 2008)
2 Application of Microorganisms for Biofuel Production
47
Enzymatic hydrolysis is a preferred procedure where cellulose is hydrolysed into
fermentable sugars and it can be catalysed by cellulase enzymes. Production of
cellulase enzymes can be done by bacteria (Clostridium, Bacillus,
Thermomonospora, Bacteriodes, Streptomyces, etc.) and fungi (Sclerotium rolfsii,
Phanerochaete chrysosporium and species of Trichoderma, Aspergillus, Penicillium). Several aspects like porosity, cellulose fibre crystallinity, lignin (which is not
fermentable) and hemicellulose content, etc. affect the hydrolysis of cellulose. Thus,
hydrolysis can be improved by reducing the cellulose crystallinity and removing
lignin and hemicellulose with an increase in porosity during the pretreatment
process.
The application of agricultural wastes or residues and bagasse (a by-product of
sugar industry) to produce bioethanol has been shown in recent studies. The major
drawback was the cost of cellulase enzymes used in the saccharification process, and
ultimately leads to increased production cost. To achieve high product yield and
reducing production cost, a lot of research has been conducted where enzyme
Fig. 2.3 Production of bioethanol from lignocellulosic biomass (adapted from Lin and Tanaka
2006; Balat et al. 2008)
2 Application of Microorganisms for Biofuel Production
47