Evaluating crude whey for bioethanol production using non‑Saccharomyces yeast, Kluyveromyces marxianus

摘要

Ethanol production from non-food substrate is strongly recommended to avoid competition with food production.Whey, which is rich in nutrients, is one of the non-food substrate for ethanol production by Kluyveromyces spp. The purposeof this study was to optimize ethanol from different crude (non-deproteinized, non-pH adjusted, and non-diluted)whey using K. marxianus ETP87 which was isolated from traditional yoghurt. The sterilized and non-sterilized wheywere employed for K. marxianus ETP87 substrate to evaluate the yeast competition potential with lactic acid and othermicroflora in whey. The effect of pH and temperature on ethanol productivity from whey was also investigated. Peptone,yeast extract, ammonium sulfate ((NH_4)_2SO_4), and urea were supplemented to whey in order to investigate the requirementof additional nutrient for ethanol optimization. The ethanol obtained from non-sterilized whey was slightly andstatistically lower than sterilized whey. The whey storage at 4 °C didn’t guarantee the constant lactose presence at longerpreservation time. Significantly high amount of ethanol was attained from whey without pH adjustment (3.9) even if itwas lower than pH controlled (5.0) whey. The thermophilic yeast, K. marxianus ETP87, yielded high ethanol between 30and 35°C, and the yeast was able to produce high ethanol until 45 °C, and significantly lower ethanol was recorded at50 °C. The ammonium sulfate and peptone enhanced ethanol productivity, whereas yeast extract and urea depressedthe yeast ethanol fermentation capability. The K. marxianus ETP87, the yeast isolated from traditional yoghurt, is capableof producing ethanol from non-sterilized and non-deproteinized substrates.