Rhodosporidium toruloides and Tetradesmus obliquus Populations Dynamics in Symbiotic Cultures, Developed in Brewery Wastewater, for Lipid Production

Biodiesel production and properties estimation from food waste and domestic wastewater by Rhodosporidium toruloides

Producing biodiesel from food waste (FW) would benefit both environment and economy. Current study investigated biodiesel production from food waste and domestic wastewater by utilizing the oleaginous yeast Rhodosporidium toruloides under non-sterile condition. The potential of biolipid production from the mixture of effluents of existing local FW treatment facilities and domestic wastewater was firstly evaluated. Then, to increase the nutrient recovery efficiency, FW hydrolysis process by crude enzymes produced from solid FWs by Aspergillus oryzae was introduced and the conditions were further optimized. The optimized hydrolysis process resulted in reducing sugar (RS) yield of 251.81 ± 8.09 mg gdryFW-1 and free amino nitrogen (FAN) yield of 7.70 ± 0.74 mg gdryFW-1 while waste oil with the RS yield of 93.54 ± 0.01 mg gdryFW-1 was easily separated without solvent usage. Compared to the hydrolysate only used, when mixed with domestic wastewater, the results showed obvious enhancement on biomass yield, biolipid yield, and wastewater treatment efficiency. The maximum biolipid yield was 29.80 ± 0.50 mg gdryFW-1 and the estimated quality of biodiesel produced from the biolipid met both EN 14214 and ASTM D6751 standards.

The draft genome sequence of Rhodosporidium toruloides strain Z11, an isolate capable of co-producing lipids and carotenoids from waste molasses

A wild-type Rhodosporidium toruloides strain Z11 which could utilize molasses to co-produce high amount of lipid and carotenoids was isolated and characterized. The genome of strain Z11 with a G + C content of 59.0% was estimated to be 22.6 Mb and contained 5290 encoded protein sequences. Among these annotated genes, the ATP citrate (pro-S)-lyase, two malic enzymes (MaeA and MaeB) and the geranylgeranyl pyrophosphate synthase play key roles for the production of lipids and carotenoids. In addition, a β-fructofuranosidase (SacA) was identified, which may contribute to the utilization of molasses.

Effect of brewery effluent inhibitors on Rhodotorula toruloides NCYC 921 cells grown in pure and mixed cultures at pH 4 and 6

The presence of inhibitor compounds in the culture medium can cause severe effects on the microorganisms cells. Brewery wastewaters present organic acids (acetic, propionic and butyric acids) which can severely affect yeast cells metabolism, when grown in pure cultures, although in mixed cultures they are able to develop. To understand the physiological changes on Rhodotorula toruloides (formerly Rhodosporidium toruloides) cells when fermenting in the presence of the organic acids present in brewery wastewater, pure and mixed cultures with the microalga Tetradesmus obliquus were performed in a synthetic medium containing the same organic acids concentrations that are present in brewery wastewater at pH 4 and 6. It was concluded that, at pH 4, the organic acids effects in the yeast cells were much more toxic than at pH 6. Moreover, mixed cultures can be an advantage over heterotrophic pure cultures as the microalga is able to contribute for the consumption of potential inhibitors for the yeast.