(57f) Production of Heavy Oil Liamocin By Aureobasidium Pullulans

Aureobasidium pullulans is a ubiquitous fungus that is well known for producing exopolysaccharide pullulan, polymalic acid (PMA), and many useful industrial enzymes such as xylanase and lipase. Some strains of A. pullulans can also produce extracellular heavier-than-water oils known as liamocins. Liamocins are esters composed of a single mannitol headgroup O-acetylated with 3 or 4 3,5-dihydroxydecanoic ester groups, and can be used as biosurfactant, antimicrobial agent against some Streptococcus spp., anti-cancer agent, and biofuels. The highest liamocin production reported to date was 22 g liamocin/L from optimized medium by strain NRRL 50384. The PKS (polyketide synthase) is reported to be involved in the biosyntheses of fatty acids and melanin in A. pullulans. However, the complete liamocin biosynthesis pathway has not been elucidated, although the genomes of several strains have been sequenced.

The objective of this research was to optimize liamocins production from various sugars, such as sucrose and glucose, in fermentation. The strain NRRL 58544 produced 9.2 g/L liamocins from 50 g/L sucrose, which was higher than 5.4 g/L previously reported using the same medium formula. Batch fermentations in shake-flasks showed that a higher liamocin production was obtained in the medium with a higher C/N ratio. Furthermore, a lower temperature stimulated oils accumulation. In general, dark/black heavy oils were produced from sucrose, because of the coproduction of melanin. In contrast, heavy oils produced from glucose by the strain NRRL 62031 had a more pleasant, light yellow color. Scale up of the fermentation process will be performed in a 1-L bioreactor with pH and temperature controls. Transcriptomics and metabolomics analyses of the fermentation under different conditions will be performed, and the results will provide a theoretical basis for genetic modifications of the metabolic pathway to further enhance liamocin production in A. pullulans.