Growth and phycocyanin production with Galdieria sulphuraria UTEX 2919 using xylose, glucose, and corn stover hydrolysates under heterotrophy and mixotrophy

The production of cell mass and phycocyanin (PC) was evaluated with the extremophile microalgae Galdieria sulphuraria 2919, under mixotrophic and heterotrophic conditions, in media supplemented with glucose, xylose, or a mixture of both sugars, and hemicellulosic and cellulosic hydrolysates from corn stover. Compared to xylose, cultivations with glucose under heterotrophic conditions showed 51%, 42%, and 66% higher specific growth rate, biomass volumetric productivity, and biomass yield, respectively. Glucose caused a suppression of xylose consumption and PC content was 54.4% lower when xylose was used, suggesting it inhibits the production of this pigment-protein. The use of hemicellulosic corn stover hydrolysates, hindered microalga growth because acetate at low concentrations (approximately 0.6 g L−1) caused inhibition of G. sulphuraria growth. The cellulosic fraction of corn stover was saccharified using cellulases to obtain a syrup containing glucose without acetate. When G. sulphuraria was cultivated under heterotrophic conditions on this syrup, the microalgae accumulated up to 165 mgPC gSolubleProtein−1.