Screening of Industrial Wastewaters as Feedstock for the Microbial Production of Oils for Biodiesel Production and High-Quality Pigments

Abstract

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 yeastRhodotorula glutiniswas 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.

Bio-Refining of Carbohydrate-Rich Food Waste for Biofuels

“…Irrespective of cultivation medium, fatty acid profiles and elongation and desaturation patterns were typical for R. glutinis and de novo lipid synthesis [43]. In line with other reports, oleic acid (C18:1) and linoleic acid (C18:2) were the main MUFA and PUFA of R. glutinis cultivated in CRFW hydrolysates [16,23,44]. Oleic acid (C18:1) accounted for ~42% in Th-cultivated R. glutinis biomass, whilst the levels were 35 and 44% lower in Ch-and Pcon cultivates, respectively.…”

“…Yeast is considered superior over other microorganisms due to high biomass growth rates, lipid accumulation capacity, fatty acid profile, and carotenoid, biopolymer and nutraceutical potential [15,16]. Although there are 600 identified yeast species, fewer than 30 species can be categorised as oleaginous with the lipidome accounting for >20% biomass and only very few produce carotenoids and biopolymers [17,18].…”

“…For instance, Yerrowia lipolytica (phylum Ascomycota) has been used for bio-refining of lipid-rich restaurant-food waste, which proved to be an excellent cultivation medium when coupled with hydrolysis of the complex sugars [19]. In contrast, the red yeast Rhodotorula glutinis (phylum Basidiomycota) has been cultivated on different wastewater media [16], food waste and municipal wastewater mixed media [20], glycerol- [15] and starch-containing wastewaters [21]. Another yeast, Cryptococcus curvatus showed higher productivity than Y. lipolytica when cultured on glucose-based media, but lipid content was 10% lower than R. glutinis cultured on food waste hydrolysates [20].…”

“…Of the total lipidome accumulated and synthesized, ≥90% is comprised solely of triacylglycerides (TAG), free fatty acids (<1%) (FFA) and steryl esters (SE) [24]. Furthermore, R. glutinis accumulate the high value bio-product β-carotene (1 kg ~ 1,600 USD) used commercially as a food colorant, nutritional supplement, cosmetic colorant, antioxidant and anticancer agent in pharmaceuticals [16].…”

Carbon concentration and oxygen availability affect lipid and carotenoid production by carob pulp syrup‐grown Rhodosporidium toruloides NCYC 921

“…The use of low‐cost substrates in media formulations may also reduce the costs of the microbial biofuels production . Carob pulp syrup has been used in media formulations for microbial lipid production .…”