In Situ Lignin Bioconversion Promotes Complete Carbohydrate Conversion of Rice Straw by Cupriavidus basilensis B-8

The valorization of lignocellulose encounters both opportunities and challenges as the lignocellulose is an abundant and intrinsically heterogeneous natural source. However, the successful design of an integrated process for complete carbon utilization of lignocellulose is limited. A classic base-catalyzed pretreatment strategy and a natural Cupriavidus strain with the capacity of lignin degradation and polyhydroxyalkanoates (HAs) biosynthesis were selected to establish a fundamental and functional module necessary to enable a new platform for lignocellulose pretreatment and waste carbon conversion. The in situ bioconversion was first introduced to the pretreatment. Specifically, selectively cleaving insensitive C-C bonds (e.g., beta-5) of lignin via a washing mechanism, Cupriavidus basilensis B-8 promoted the digestibility of the rice straw to realize almost complete carbohydrate conversion, yielding 984.2 mg g(-1) of reducing sugar when combined with alkaline pretreatment. A demonstrated concentration of PHA (482.7 mg L-1) was obtained from the conversion of the removed lignin in ligninolytic bacteria. The integrated molecular conversion mechanisms of lignin in bacteria were further elucidated. Our work provides a novel perspective for biorefinery design.