Author:

Keywords:

Single Cell Oils, Biofuel, yeast, waste substrate

Abstract:

While several industrial processes for the production of biofuels have been well established in the last decade, there is still a great demand for new and economic routes to biofuels and to bulk and fine chemicals from renewable resources which are not in competition with food or animal feed. In our opinion it will be possible to overcome these problems and produce said chemicals from organic waste materials or by-products in future using microbial or enzymatic processes. A summary of our previous experimental work on the use of oleaginous yeasts for the production of intracellular triglycerides, so called "single cell oils". Deproteinized whey concentrates were successfully used as waste substrates for yeast strains able to enzymatically hydrolyse lactose. Other substrates of interest in future are glycerol e.g. from biodiesel production or lignocellulose derived carbohydrates. In all cases the "single cell oil" will be produced in the stationary phase of growth under nitrogen limitation. Sequential batch processes can be a key to a more economic biomass production. After downstream processing the "single cell oils" can be used either as biofuel or for the subsequent production of bulk and fine chemicals. Valorisation of other ingredients such as proteins as well as of the resulting biomass e.g. by methanisation can add to the eventual economical feasibility. Challenges which are still open are the development of easy to perform and economic methods for the extraction and separation of the valuable ingredients. The unfavourable side production of carbon dioxide during the fermentation could be overcome e.g. by combining the yeast cultivation with a closed algae process consuming said carbon dioxide and leading to similar products.