Tuesday, April 30, 2013
Exhibit Hall
Microbial oils are an important step towards renewable transportation fuels. Oleaginous yeasts have doubling times of hours rather than days, and are less susceptible to contamination than microalgae. While yeasts can only be cultivated heterotrophically, faster growth and decreased risk of contamination may overcome this limitation. Efforts are underway in our laboratory to identify novel oleaginous yeast species that are able to convert various types of biomass hydrolysates to lipids. We have identified several novel oleaginous species and strains in a survey of yeasts from the Phaff Yeast Culture Collection as well as our new isolates from the rain forest in Indonesia. Twenty-six strains that accumulated over 30% lipids, 21 additional Indonesian strains, and two controls were screened for sugar utilization and toxin tolerance in 8mL media. Eleven of these strains could grow in media containing glucose and/or xylose in the presence of HMF and furfural. We selected six yeast strains to scale up to 100mL cultures in a define nitrogen-limiting media: Candida kazuoi-like new species UCD-FST 10-784, Cryptococcus magnus UCD-FST 10-900, C. sagamina-like new species UCD-FST 10-1002, C. intermedia UCD-FST 11-455, C. tenuis UCD-FST 11-461, and C. intermedia UCD-FST 11-472. Total lipid content was analyzed by Nile red and gravimetric assays. Most of these yeasts accumulated more lipids in the presence of xylose as carbon source than in glucose. Oleaginous yeasts that produces higher cell mass accumulated less lipids. Studies of sugar depletion, lipid accumulation and growth profile in synthetic hydrolysates are currently underway.