Bioconversion of oxygen-pretreated Kraft lignin to microbial lipid with oleaginous Rhodococcus opacus DSM 1069

Abstract

Kraft lignin (KL) from black liquor is an abundantly available, inexpensive aromatic resource that is regarded as a low value compound by the pulp and paper industry, necessitating the development of new applications. Current work proposes an innovative KL utilization strategy that connects partial lignin degradation with lipid production in oleaginous Rhodococcus. Results showed poor bacterial growth when KL was used directly as a substrate. On the other hand, when KL recalcitrance was reduced by oxygen-pretreatment (O₂-KL), Rhodococcus opacus DSM 1069 was capable of utilizing this material and in turn accumulated lipids. The maximum lipid yield was measured to be 0.067 mg ml⁻¹ at 36 h of growth and these lipids were mainly composed of palmitic (46.9%) and stearic (42.7%) acids.