LIPIDS PRODUCTION FROM LIGNOCELLULOSIC HYDROLYZATES BY THE OLEAGINOUS YEAST CRYPTOCOCCUS CURVATUS

Biomass sugars are a versatile platform for the production of a number of biobased products. Microbial lipids, obtained by means of oleaginous microorganisms, represent one conversion option. Most of the lipids accumulated in oleaginous microorganisms, are triglycerides which can be used as raw material in various oils-based processes including, for instance, the production of biodiesel and bioplastics. Biomass sugars, obtained from residual straws or lignocellulosic crops such as Arundo donax, contain both C5 and C6 compounds that must be effectively converted to make the overall process sustainable. Among the oleaginous microorganisms, the yeast Cryptococcus curvatus has attracted much attention thanks to the capacity to use both C5 and C6 sugars. In the present study Cryptococcus curvatus was investigated for the production of lipids from lignocellulosic hydrolysates of steam pretreated Arundo donax. The fermentation set- up was first optimized by using synthetic media. In particular, a number of parameters were investigated: the carbohydrates composition and concentrations, the carbon/nitrogen ratio and the nutrients composition by using the response surface methodology (RSM) analysis. Finally, a fed-batch process was implemented for the fermentation of Arundo donax hydrolysates, yielding a total lipid content of 64% of the dry cell weight.