The production of biodiesel has notably increased over the past decade. Currently, plant oil is the main feedstock for biodiesel production, but, due to concerns related to the competition with food production, alternative oil feedstocks have to be found. Oleaginous yeasts are known to produce high amounts of lipids, but no integrated process from microbial fermentation to final biodiesel production has reached commercial realization yet due to economic constraints. Therefore, growth and lipid production of red yeast Rhodotorula glutinis was tested on low-cost substrates, namely, wastewaters from potato, fruit juice, and lettuce processing. Additionally, the production of carotenoids as high-value by-products was examined. All evaluated wastewaters met the general criteria for microbial lipid production. However, no significant increase in lipid content was observed, probably due to lack of available carbon in wastewaters from fruit juice and lettuce processing, and excess of available nitrogen in potato processing wastewater, respectively. During growth on wastewaters from fruit juice and lettuce processing the carotenoid content increased significantly in the first 48 hours. The relations between carbon content, nitrogen content, and carotenoid production need to be further assessed. For economic viability, lipid and carotenoid production needs to be increased significantly. The screening of feedstocks should be extended to other wastewaters. 1. Introduction In the course of the ongoing endeavor to find alternatives for fossil energy, significant effort has been put into expanding the utilization of renewable resources. Accordingly, there is already a considerable variety of products and commodities based on renewable resources available, which are fed both into energetic and material utilization pathways. Especially in the field of energy supply, the progressive depletion of conventional fossil fuels along with a worldwide growing demand for petroleum-based fuels has put high pressure on science and industry to find alternative energy sources [1]. Over the last decade, research has successfully managed to develop a broad range of sustainable and cost-effective techniques to produce renewable energy, one of them being the conversion of biomass into biofuels. While biofuels in general also include, for example, firewood or woodchips for direct combustion and use for heating or electricity production, liquid biofuels are mainly researched in order to replace conventional liquid fuels like diesel and petroleum [1]. Within this class, biodiesel is a
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