Cellobionate production from sodium hydroxide pretreated wheat straw by engineered Neurospora crassa HL10

Authors: WANG, JIAJIE - University Of California, Davis; Kasuga, Takao; FAN, ZHILLIANG - University Of California, Davis

Submitted to: Bioprocess and Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2024
Publication Date: 7/12/2024
Citation: Wang, J., Kasuga, T., Fan, Z. 2024. Cellobionate production from sodium hydroxide pretreated wheat straw by engineered Neurospora crassa HL10. Bioprocess and Biosystems Engineering. Volume 47, pages 1683–1690, (2024). https://doi.org/10.1007/s00449-024-03061-w.
DOI: https://doi.org/10.1007/s00449-024-03061-w

Interpretive Summary: Lignocellulosic biomass is a renewable, low-cost, and abundant source for the production of biofuels. Several fungal pathogens are capable of decomposing lignocellulosic materials to sugar, therefore, have the industrial potential for bioenergy production. We have been developing fungal mutants that are able to convert lignocellulosic material to cellobionate (sugar acid). When laccase-producing engineered strain was used to decompose purified cellulose, an exogenous redox mediator was needed to achieve a high yield conversion. We found that when NaOH-pretreated wheat straw was used as the substrate, the exogenous redox mediator addition was unnecessary because the lignin in the pretreated wheat straw can serve as the redox mediator.

Technical Abstract: This paper describes the production of cellobionate from the cellulosic substrate by the strain Neurospora crassa HL10. When Avicel was used as the substrate, the system was redox mediator limiting. The addition of an artificial redox mediator led to higher cellobionate addition. When NaOH-pretreated wheat straw was used as the substrate, the exogenous redox mediator addition was unnecessary because the lignin in the pretreated wheat straw can serve as the redox mediator. However, the laccase production level produced by strain HL10 on pretreated wheat straw was relatively low, which led to the slow production of the cellobionate. Cycloheximide successfully induced high-level laccase production in N. crassa HL10. With the addition of 0.3uM of cycloheximide, the strain HL10 produced 57 mM cellobiose from pretreated wheat straw which contained 20g/L equivalent cellulose without any enzyme or redox mediator addition. The conversion time was shortened from 8 days to 6 days. The cellulose conversion was about 94%, and the cellobinate yield from the consumed cellulose was 97%.