Co-cultivation of Lipomyces starkeyi and Acinetobacter baylyi for the production of microbial lipids from lignocellulosic hydrolysates

The growth of Acinetobacter baylyi and Lipomyces starkeyi was investigated individually and in a co-culture in a minimal medium (MM) in the presence of vanillin, syringaldehyde, para-hydroxybenzaldehyde (PHB), furfural and hydroxymethylfurfural (HMF), to understand the growth and lipid accumulation capability. The MM, which was developed in our laboratory, significantly reduced the medium cost for lipid production by L. starkeyi from $12.68 per gallon lipids to $3.11 per gallon lipids with the carbon source representing the remaining major cost factor. A. baylyi failed to grow in the MM but grew in the modified Suutari medium (MSM). L. starkeyi showed a decreased growth in the presence of a mix of 0.1 g/L and 0.25g/L of furfural, HMF, PHB, vanillin, and syringaldehyde in comparison to the growth in the MM without these inhibitors and completely failed to grow when they were present at the 0.5 g/L concentrations. The co-culture of L. starkeyi and A. baylyi in the MM resulted in the maximum cell concentration and lipid production of 9.72 g/L and 5.04 g/L; 9.72 g/L and 4.90 g/L; and 9.24 g/L and 4.65 g/L for the initial inhibitor concentrations of 0.1 g/L; 0.25 g/L and 0.5 g/L, respectively. Almost complete consumption of the inhibitors was observed when they were added at 0.1 g/L and 0.25 g/L concentrations. However, at initial inhibitor concentrations of 0.5 g/L, the inhibitors were first taken up but then released back into the media when the co-culture reached the stationary phase.