Valorization of industrial lignin to value-added chemicals by chemical depolymerization and biological conversion

•Integration of chemical and biological processes for valorization of waste lignin.•State-of-art information of thermochemical route –first step of valorization.•Advances and key challenges of biological conversion – second step of valorization.•Bridging the gap between thermochemical and biological processes.•Value-added products from waste lignin: vanillin, muconate, PHAs, lipids.