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ARS Home » Plains Area » Lincoln, Nebraska » Wheat, Sorghum and Forage Research » Research » Publications at this Location » Publication #305574
Title: Simultaneous conversion of all cell wall components by oleaginous fungus without chemi-physical pretreatment

Author
item XIE, SHANGXIAN - Texas A&M University
item QIN, XING - Texas A&M University
item CHENG, YANBING - Texas A&M University
item LASKAR, DHRUBOJYOTI - Washington State University
item QIAO, WEICHUAN - Texas A&M University
item SUN, SU - Texas A&M University
item REYES, LUIS - Texas A&M University
item WANG, XIN - Texas A&M University
item DAI, SUSIE - Texas Agrilife Research
item Sattler, Scott
item KAO, KATY - Texas A&M University
item YANG, BIN - Washington State University
item ZHANG, XIAOYU - Huazhong Agricultural University
item YUAN, JOSHUA - Texas A&M University

Submitted to: Green Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2014
Publication Date: 3/1/2015
Citation: Xie, S., Qin, X., Cheng, Y., Laskar, D., Qiao, W., Sun, S., Reyes, L.H., Wang, X., Dai, S.Y., Sattler, S.E., Kao, K., Yang, B., Zhang, X., Yuan, J.S. 2015. Simultaneous conversion of all cell wall components by oleaginous fungus without chemi-physical pretreatment. Green Chemistry. 17: 1657-1667. doi:10.1039/C4GC01529K.

Interpretive Summary: Biomass, the cell wall material from leaves and stalks of plants, has been proposed to be a renewable resource for the production of biofuels. There are three main components of biomass: cellulose, hemicellulose and lignin. Lignin represents a major challenge for conversion of biomass to biofuels, because its presence impedes this process. As a potential system to produce biodiesel or jet fuels, we studied an oil-synthesizing fungus that is able to grow on biomass. We examined the ability of the fungus to consume sorghum biomass and produce oils. We grew this fungus on biomass from normal sorghum plants and mutant lines with reduced lignin levels. The study clearly showed that the fungus consumed lignin along with the other biomass components. In addition, the fungus consumed more biomass and produced more oil when grown on reduced lignin biomass. This reduced lignin biomass did not require any treatment to make it digestible for the fungus, unlike normal sorghum biomass. Combining this fungus with sorghum mutants that have reduced lignin levels may represent a system to produce biodiesel and jet fuels from biomass.

Technical Abstract: Lignin utilization during biomass conversion has been a major challenge for lignocellulosic biofuel. In particular, the conversion of lignin along with carbohydrate for fungible fuels and chemicals will both improve the overall carbon efficiency and reduce the need for chemical pretreatments. However, few biomass-converting microorganisms have the capacity to degrade all cell wall components including lignin, cellulose, and hemicellulose. We hereby evaluated a unique oleaginous fungus strain Cunninghamella echinulata FR3 for its capacity to degrade lignin during biomass conversion to lipid, and the potential to carry out consolidated fermentation without chemical pretreatment, especially when combined with sorghum (Sorghum bicolor) bmr mutants with reduced lignin content. The study clearly showed that lignin was consumed together with carbohydrate during biomass conversion for all sorghum samples, which indicates this organism has the potential for biomass conversion without chemical pretreatment. Even though dilute acid pretreatment of biomass resulted in more weight loss during fungal fermentation than untreated biomass, the lipid yields were comparable for untreated bmr6/bmr12 double mutant and dilute acid-pretreated wild-type biomass samples. The mechanisms for lignin degradation in oleaginous fungi were further elucidated through transcriptomics and chemical analysis. The studies showed that in C. echinulata FR3, Fenton Reaction may play an important role in lignin degradation. This discovery is among the first to show that a mechanism for lignin degradation similar to ones found in white and brown rot basidiomycetous fungi exists in an oleaginous fungus. This study suggests that oleaginous fungus such as C. echinulata FR3 can be employed for complete biomass utilization in a consolidated platform without chemical pretreatment, or can be used to convert lignin waste into lipids.