Lignin Degradation in the Production of Bioethanol – A Review

Lignin is the principal impediment in the production of biofuel from different lignocellulosic sources through hydrolysis, saccharification and fermentation route. The two main types of treatment for lignin separation from the other main constituent plant materials, hemicellulose and cellulose, are biodegradation and the chemical degradation including base‐catalyzed, acid‐catalyzed, ionic liquids‐assisted lignin depolymerization. Severe reaction conditions, such as high pressure, high temperature and extreme pH, are being in practice for chemical degradation and result in the requirement of specially designed reactors. This leads to high costs of facility and handling along with the inadvertent generation of toxins. Biological degradation seems to be widespread and cost effective if enzymes degrading lignin could be produced by isolation of fungi. Bacterial strains could also be prepared that produce the lignin‐splitting enzyme laccase. The present article reviews the available processes for lignin degradation during lignocellulosic conversion of ethanol and discusses the research gaps in these fields.