High titer fatty alcohol production in Lipomyces starkeyi by fed-batch fermentation

Abstract

Extracellular production of long chain fatty acid-based products, such as fatty alcohols, are being investigated as intermediates amenable to separations and catalytic upgrading to hydrocarbon fuels. We previously demonstrated that the oleaginous yeast, Lipomyces starkeyi expressing the fatty acyl-CoA reductase (FAR) gene from Marinobacter aquaeolei VT8, produced up to 770 mg/L of fatty alcohols. The FAR genes expressed in L. starkeyi transformants exhibited different fatty alcohol production levels. To better understand fatty alcohol production and potentially further increase fatty alcohol titer and yields, we investigated the expression levels, copy numbers, and enzymatic activities of the expressed FAR genes. Our results showed that fatty alcohol production is dependent on the above factors for higher titers of fatty alcohols. Fatty alcohol titer was further increased in the highest producing transformant by testing different basic process configurations (batch and fed-batch) with different initial nitrogen concentrations and feed rates. In fed-batch, a maximum of 4.2 g/L fatty alcohols were produced in 5-L bioreactor. The oleaginous yeast L. starkeyi can produce high titers of fatty alcohols particularly when periodically fed glucose and nitrogen.

Keywords

• Oleaginous yeast
• Lipomyces starkeyi
• Fatty alcohols
• Fed-batch fermentation