Recycling microbial lipid production wastes to cultivate oleaginous yeasts

• Spent cell mass hydrolysates supported cell growth of various oleaginous yeasts.
• Spent cell mass hydrolysates used as nutrients for lipid production.
• Recycling both cell mass and spent water improved lipid production efficiency.
• Spent cell mass hydrolysates improved lipid production from corn stalk hydrolysates.
• Lipid samples had similar fatty acid compositional profiles to those of vegetable oils.

To reduce wastes and the costs of microbial lipid production, it is imperative to recycle resources, including spent cell mass, mineral nutrients and water. In the present study, lipid production by the oleaginous yeast Rhodosporidium toruloides was used as a model system to demonstrate resources recycling. It was found that the hydrolysates of spent cell mass were good media to support cell growth of various oleaginous yeasts. When serial repitching experiments were performed using 70 g/L glucose and the hydrolysates alone as nutrients, it produced 16.6, 14.6 and 12.9 g/L lipids, for three successive cycles, while lipid titre remained almost constant when spent water was also recycled. The cell mass hydrolysates could be used as equivalents to the mixture of yeast extract and peptone to support lipid production from corn stalk hydrolysates. Our results showed efficient recycling of lipid production wastes and should be helpful to advance microbial lipid technology.

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