(399f) Single Cell Protein Production From Glycerol Residues Discharged From Biodiesel Production Plant

Glycerol is now considered as the major byproduct from biodiesel manufacture. Nowadays, the application of glycerol is very limited. In the near future, biodiesel production may suffer from glycerol surplus if there is no sustainable solution for glycerol utilization. In a large commercial biodiesel plant, crude glycerol often enters purification process which eventually yields highly purified glycerol for applications in pharmaceutical and cosmetic industries. Nonetheless, a large amount of purified glycerol is still a surplus for pharmaceutical and cosmetic industries. Using the biotechnology technique to convert glycerol to the value-added product has been brought into attraction. It is well known that Hansenula polymorpha consume glycerol for both carbon and energy sources. Under aerobic condition, glycerol is usually converted by glycerol kinase into glycerol-3-phosphate (G3P), which is then oxidized to dihydroxyacetone phosphate (DHAP) by a membrane-bound G3P dehydrogenase before entering a central metabolic pathway. In this work, batch fermentation of H. polymorpha IBGE HP-5001 in YE-glycerol medium using different glycerol samples discharged from purification process of biodiesel production plant has been studied in a 5-L stirred tank bioreactor. It was found that H. polymorpha IBGE HP-5001 was capable of consuming glycerol in glycerol containing discharged streams for biomass production. The highest cell biomass production was observed in the fermentation of YE-glycerol media containing 5% pharma glycerol and 5% technical glycerol while low biomass yield was obtained in the fermentation of YE-glycerol media containing 50% residual glycerol and 9% crude glycerol due to high osmolarity. In order to reduce the production cost, the medium containing yeast extract as an enriched organic N-source was replaced by the minimal salts medium. Due to a large amount of salts remained untreated in the medium, an inorganic N-source ((NH₄)₂SO₄) with supplemented salts (MgSO₄ and KH₂PO₄) even caused higher osmotic pressure as compared to those in the YE-glycerol medium. This resulted in low biomass production. Salt removal from discharged glycerol is recommended to obtain the higher cell biomass production.