Assessment of lignocellulose hydrolysate component consumption by co-culture of Acinetobacter baylyi ADP1 and Lipomyces starkeyi Y-1389.

One of the major uses of petroleum products is transportation fuel such as gasoline and diesel, consumption of which substantially contributes to global warming. Oleaginous microorganisms capable of growing on lignocellulose hydrolysates serve as sustainable alternatives to hydrocarbon derived fuels. Co-culturing of two oleaginous microorganisms Acinetobacter baylyi ADP1 and Lipomyces starkeyi Y-1389 potentially allow us to overcome limitations of each of them, i.e., a relatively low lipid productivity for the former and a sensitivity to lignin hydrolysate products of the latter. This study investigated the ability of L. starkeyi Y-1389 to produce lipids alone or in co-culture with A. baylyi ADP1, specifically examining the influence of lignin-derived inhibitors on this process. Microorganisms were cultured in a mineral medium supplemented with sugar mixtures (glucose and xylose) and non-sugar components (acetate, formate, furfural, 5-hydrox ymethylfurfural, p-hydroxybenzaldehyde, syringaldehyde and vanillin), which are typically produced during lignocellulose hydrolysis. Both microbes were shown to tolerate some levels of furfural (up to 0.5 g/l for yeasts and 0.1 g/l for bacteria), 5-hydroxymethylfurfural (up to 0.5 g/L for both), p-hydroxybenzaldehyde (up to 0.25 g/1 for bacteria and 0.5 g/ for yeasts), syringaldehyde (up to 0.5 g/l for both) and vanillin (up to 0.1 g/l for yeasts and 0.5 g/l for bacteria), which typically serve as potential growth inhibitors. Formate and acetate, also common components of lignocellulose hydrolysates, was shown to suppress lipid production in A. baylyi ADP1 but not L. starkeyi Y-1389. During 144 h fermentation all potential inhibitors as well as acetate and formate were completely consumed by co-cultures. While lipid content in co-culture (32-36% of dry biomass) was comparable to L. starkeyi Y-1389 monoculture (32-40%), without significant advantages observed for co-culture in terms of yield, the co-culture exhibited higher resistance to a lignin-derived inhibitor mix compared to the yeast monoculture. This suggests that A. baylyi ADP1 effectively detoxifies the medium, allowing for better overall performance under inhibitory conditions. The results also suggest that wood hydrolysates are more favorable for lipid production using the A. baylyi ADP1 and L. starkeyi Y-1389 co-culture than hydrolysates of herbaceous plants indicating that a co-culture is a better choice for biotechnological production of lipids when wood hydrolysate is used. Our findings indicate that despite bacterial dominance and suppression of A. baylyi lipid production by acetate and formate, the co-culture approach is a promising strategy for biotechnological lipid production, particularly when utilizing wood hydrolysates, warranting further investigation into optimizing these microbial consortia.