Studies on production of ethanol from cheese whey using Kluyveromyces marxianus

Whey, the residue remaining following cheese/casein production, represents a major disposal problem for the dairy industry as this has been considered as a highly polluting stream. Typically, whey contains lactose, proteins and fat. Due to lactose content, liquid whey can be considered as a cheap resource for production of bio-ethanol. Bio-ethanol can help to meet global fuel demand in the present scenario of depleting fossil fuel reserve. Direct fermentation of cheese whey or whey permeate yields low ethanol concentration due to poor lactose content, thus making the process uneconomical. Cheese whey powder (CWP), a dried and concentrated form of cheese whey, containing high concentration of lactose, can be an attractive source for ethanol production. In the present study, ethanol was produced from CWP with initial lactose concentration of 150 g/L at a temperature of 35°C and pH 4.5 using lactose positive microorganism, Kluyveromyces marxianus NCIM 3217. Maximum ethanol production was found to be 43.71 g/L and almost all the lactose was consumed within 72 h. Maximum biomass concentration at the end of fermentation was found to be 6.02 g/L. From the experimental data, it was found that the microbial growth followed Monod kinetic model. Ethanol production using K. marxianus NCIM 3217 was found to follow Luedeking – Piret equation and it was mixed-growth-associated. Thus, cheese whey powder could be an attractive substrate for bio-ethanol production and and hence can solve the environmental pollution problem created by whey surplus.