Biological conversion of lignin and its derivatives to fuels and chemicals

Lignocellulosic biomass, which is one of the most abundant and renewable sources for the production of clean fuels and chemicals, consists mainly of cellulose, hemicellulose and lignin. The conversion of cellulose and hemi-cellulose to value added products has been extensively carried out over the last few decades. However, the direct conversion of lignin, the second most abundant aromatic polymer on earth, is challenging due to its heterogeneity and low reactivity. Most of the lignin produced in the pulp and paper industry is used as a fuel to generate heat and electricity. Recently, the chemical or biological conversion of lignin is considered one of the most promising technologies for the production of high-value products. The biological conversion of lignin has several advantages over the chemical co version route in terms of low operating costs, high specificity, and the absence of harsh operating conditions and hazardous chemicals. The present review summarizes recent studies on biological valorization of lignin to value-added products. Additionally, this review emphasizes the various lignin extraction techniques, catabolic pathways involved, necessary enzymes, and the major challenges of this process.