Adsorbed oils as ABE fermentation substrate

Bleaching earth is a mineral adsorber which is applied in tremendous amounts for purification of fats and oils. The world market of this adsorber material is estimated to approximately 625,000 tons per year. The bleaching earth is used to remove undesired by-products from the raw material which are concomitantly released from the plant material during the applied disintegration procedures. Such by-products can be summarized as chlorophyll, carotinoides, trace metals, soaps, phospholipids, and corresponding oxidation products. However, after separation of the bleached oil from the bleaching earth the adsorber still contains a great amount of oil, which ranges usually from 20-40 % of the minerals’ dry mass. Its utilization as additive for animal feeds, biogas plants or the cement industry was established as well as further extraction to obtain the remaining oil fraction, respectively.
Alternatively, the loaded bleaching earth can be utilized as a fermentation substrate to obtain valuable commodities as such as acetone, butanol or ethanol. Thus, a higher added value of the subsequent adsorber usage is established.
Our research is focused on the recycling of oil loaded bleaching earth, which was previously used within palm oil purification processes. We are interested in the anaerobic fermentation of the remaining palm oil fraction to the corresponding ABE compounds and fatty acids, whereas the latter shall be serve as building blocks for the synthesis of novel polymers. The production process is based on the hydrolysis of the oil to glycerol and fatty acids with subsequent or simultaneous biotransformation of the glycerol to ethanol, butanol and acetone. For this, three approaches will be presented: a) fermentation of the adsorbed oil by lipolytic Clostridia strains, without further treatment of the adsorber, b) pre-treatment of the adsorber with lipases prior to fermentation of the supernatant, and 3) co-fermentation of Clostridia sp. with lipolytic yeast.
The project is funded under No. 22023008 by the Agency of Renewable Resources / the Federal Ministry of Food, Agriculture and Consumer Protection.