Abstract
BackgroundMicrobial lipids have been emerging as a sustainable alternative to vegetable oils and animal fat to produce biodiesel and industrial relevant chemicals. The use of wastes for microbial processes can represent a way for upgrading low value feedstock to high value products, addressing one of the main goals of circular economy, the reduction of wastes by recycling. Two oleaginous yeasts, Rhodosporidiobolus azoricus and Cutaneotrichosporon oleaginosum, were used in this study to demonstrate the feasibility of the proposed approach. ResultsIn this study wastes from industrial food processing, as pumpkin peels and syrup from candied fruits manufacture, were used for yeast cultivation and for lipids production. Evaluation of growth and sugar consumption revealed marked differences between the yeasts in capacity to utilize sucrose and glucose, the main sugars present in the feedstock. In particular, we observed an unexpected limitation in glucose metabolism on mineral media by R. azoricus. Both species showed ability to grow and accumulate lipids on media exclusively composed by undiluted pumpkin peels hydrolysate, and R. azoricus was the best performing. By a two-stage process carried out in bioreactor, this species reached a biomass concentration of 45 g/L (dry weight) containing 55% of lipids, corresponding to a lipid concentration of 24 g/L, with a productivity of 0.26 g/L/h and yield of 0.29 g lipids per g of utilized sugar. These values are close to the highest reported so far from organic wastes. ConclusionsWastes from industrial food processing were sufficient to completely support yeast growth and to induce lipid accumulation. This study provides strong evidence that the concept of valorisation through the production of lipids from the complete metabolism of nutrients present in agro-industrial wastes by oleaginous yeasts is promising for implementation of biotechnological processes in a circular economy contest.
Using agro-industrial wastes for mixotrophic growth and lipids production by the green microalga Chlorella sorokiniana
