A sustainable use of low-cost raw substrates for biodiesel production by the oleaginous yeast Wickerhamomyces anomalus

Over the past decade, the increasing demand of vegetable oils for biodiesel production has highlighted the need for alternative oil feedstocks that do not compete with food production. In this context, the combined use of agro-industrial wastes and oleaginous microorganisms could be a promising strategy for sustainable biodiesel production. The present investigation involves the performance of the oleaginous yeast Wickerhamomyces anomalus strain EC28 to produce lipids from different agro-industrial wastewaters (i.e., deproteinized cheese whey, olive mill wastewater, and wastewaters from confectionary industries) and waste frying oils (i.e., waste oil from frying fish, waste oil from frying potato and waste oil from frying meat). Results indicated that this strain can adequately grow on agro-industrial wastewater-based media and produce substantial amounts of lipids [up to 24%, wt/wt in deproteinized cheese whey-based medium and olive mill wastewater-based medium (75%, v/v in water)] of similar fatty acid composition to that of the most commonly used vegetable oils in the biodiesel industry. However, the addition of frying oils to the culture media resulted in a significant decrease in total lipid content, probably due to excess of available nitrogen released from meat, fish, and potato into the frying oil. The estimated properties of the resulting biodiesels, such as SV (190.69-203.13), IV (61.77-88.32), CN (53.45-59.32), and CFPP (-0.54 to 10.4), are reported, for the first time, for W. anomalus and correlate well with specified standards. In conclusion, W. anomalus strain EC28, for which there is very limited amount of available information, might be regarded as a promising candidate for biodiesel production and additional efforts for process improvement should be envisaged.