1-03: Feedstock Lignin Modification Enhances Oleaginous Fungus Conversion of Sorghum Biomass

We developed a new platform for converting biomass to lipid by integrating feedstock lignin modification and oleaginous fungi Cunninghamella echinulata FR3.  The brown midrib (bmr) sorghum mutants with modified lignin were used as the feedstock for conversion into lipid using C. echinulata FR3. The platform was optimized for the enzyme and solid loading to achieve both semi-solid state fermentation and liquid fermentation. Fungal pelletization and growth were also optimized to maximized the lipid yield. Our initial results showed that over 50% percent of the bmr6-bmr12 double mutant sorghum were degraded in 6 days by C. echinulata FR3, 14% higher than that of wild type sorghum. Biomass and lipid yield of C. echinulata FR3 in double mutant were increased 27.5% and 13.8% compared to that in wild type respectively. We also found that 29.2% of the lignin from bmr6-bmr12 double mutant was degraded by C. echinulata FR3 in 6days, while only 15.9% lignin in wild type were degraded. The results indicated that both lignin and carbohydrate from the biomass were well converted into lipid in the mutant lines. This correlates with our findings that C. echinulata FR3 can secret cellulase and xylanase and have capacity to degrade aromatic compounds. Our result also showed C. echinulata FR3 gave higher biomass and lipid yield in double mutant as compared to those in diluted-acid pretreated wild type. Overall, our results provided strong evidence that C. echinulata FR3 conversion of sorghum mutants with reduced lignin content can provide an effective platform for biomass-based lipid production.