Screening of oleaginous yeast for lipid production using rice residue from food waste as a carbon source

Rice residue from food waste contained of starch as a mainly component which could be either hydrolyzed to be fermentable sugars or directly used as a carbon source for the growth and high value metabolites production by various microorganisms. Therefore, this study focused on the utilization of rice residue and rice residue hydrolysate from food waste as a carbon source for the growth and lipids production of oleaginous yeast. Rice residue obtained from canteen of the Faculty of Agro-Industry, Chiang Mai University, Thailand. It composed of moisture content (76.68±0.55%), crude fat (1.76±0.47%), crude protein (3.04±0.06%), ash content (0.46±0.07%), and carbohydrate content (18.05±0.01%), respectively. Rice residue was then subjected to enzymatic hydrolysis using α-amylase and amyloglucosidase (AMG), resulting the maximal reducing sugars of 168.02±0.02 g/L. The screening of oleaginous yeast from flowers and leaves samples from Doi-Inthanon National Park, Faculty of Agro-Industry, Chiang Mai University, the culture collection of the Thailand Institute of Scientific and Technological Research (TISTR) and the Division of Biotechnology, Faculty of Agro-Industry, Chiang Mai University were investigated. Sixty-seven isolates were obtained, and only four isolates were identified as oleaginous yeast because of containing high lipids content more than 20% (w/w), when glucose or rice residue hydrolysate was used as a carbon source. Those oleaginous yeasts were identified as Rhodotorula sp. C7, Rhodosporidium paludigenum C10, and the new isolate TC32, respectively. Their growths and lipid productions were compared with Diozegia sp. TISTR5792. The results showed that, C7, C10, TISTR5792 and TC32 produced the maximal lipids content of 24.26±0.56, 23.69±0.91, 22.43±1.09 and 23.07±0.80% (w/w) when cultivated in the basal medium supplemented with enzymatic-rice residue hydrolysate. Surprisingly, we found that TISTR5792 and TC32 could grow well in the medium supplemented with rice residue "> (without hydrolysis) and showed lipids content of 18.41±0.10 and 21.67±0.02% (w/w), respectively. These results indicated that rice residue from food waste shows a high potential to be an effective carbon source for the growth and lipid production of the selected oleaginous yeasts.