Sophorolipid biosynthesis by Candida bombicola from industrial fatty acid residues

YeastCandida bombicola is known to produce sophorolipids from a variety of saccharic and lipidic feed-stocks. In the current study, the influence f fatty acid carbon chain length, unsaturation, source of low-cost industrial lipid feed-stocks, and nickel content in lipid feed-stocks on sophorolipid roduction by C. bombicola were investigated. Saturated and monounsaturated C18 fatty acid gave the highest levels of sophorolipid production hile fatty acids with more than one site of unsaturation gave much lower yields. Sophorolipid production was reduced when shorter (≤C16) and onger (≥C20) fatty acids were fed. The possibility of exploiting low-cost industrial wastes or by-products for sophorolipid production by batch r fed-batch processes was investigated. Tallow fatty acid residue was the best lipid feed-stock for sophorolipid production (120 g/L, fed-batch ultures), while coconut fatty acid residue resulted in the lowest production (40 g/L, fed-batch cultures). Co-feeding coconut fatty acid residue with ther feed-stocks improved its substrate value in batch cultures. C. bombicola was tolerant to nickel contamination of up to 112.5 mg/L during ophorolipid production. Nickel contaminated stearic fatty acid residue was transformed to value added sophorolipid product while nickel was equestered primarily in biomass for safe removal and recovery. Sophorolipid product obtained from nickel contaminated lipid wastes had low ickel levels (<5 mg/L) that could allow its use in low-end consumer products and household applications. 2006 Elsevier Inc. All rights reserved.