Modelling of the Citric Acid Production from Crude Glycerol by Wild-Type Yarrowia lipolytica DSM 8218 Using Response Surface Methodology (RSM)

Abstract

Crude glycerol is the main by-product of the biodiesel manufacturing industry (10% w/w). Its use as a substrate in microbial fermentations is a concrete strategy to efficiently address its market surplus. In this study, the conversion of crude glycerol to citric acid, a key biochemical in the emerging bioeconomy, by a wild-type yeast Yarrowia lipolytica DSM 8218 was modelled using the Response Surface Methodology. The model relates C/N mass ratio and crude glycerol concentration to maximize the citric acid yield in flask scale using two different N sources, yeast extract and ammonium sulphate. Under the optimal conditions (yeast extract, C/N 141, glycerol 33 g/L), the conversion yield was 0.249 g/g. The optimal conditions were used for up-scaling a fed-batch fermentation in a 2 L bioreactor highlighting a metabolic shift from mannitol to citric acid when high stirring rates were applied (800 rpm). In these conditions, a morphic transition from pseudo-mycelial form to round-shaped yeast-like cells was observed too.

Optimized conversion of wheat straw into single cell oils by Yarrowia lipolytica and Lipomyces tetrasporus and synthesis of advanced biofuels

“…Furthermore, as found in SYN medium, less than 10% mannitol was produced along with 3 unidentified compounds, likely belonging to the polyol groups or organic acid groups. Similar results were found by Giacomobono et al [33], with Yarrowia lipolytica ATCC 46483. The authors reported mannitol and citric acid production using glycerol as the sole C source.…”

“…Moderate amounts of mannitol in the range 1.3-5.8 gL -1 were also detected. Some authors described the production of citric acid by Y. lipolytica strain DSM 8218 [33], erythritol, mannitol, and arabitol using different Y. lipolytica strains [34], isocitrate, using the strain VKM Y-2373 [35], alpha-ketoglutarioc acid using the strain A8 [36], and acetic acid using 6 different Y. lipolytica strains [37]. Although the production of mannitol was already observed in several Y. lipolytica strains, no specific data were reported so far for the strain DSM 8218 grown on sugars and the results presented in this paper enlarge the knowledge base of this microorganism.…”

Growth Response of Non-Conventional Yeasts on Sugar-Rich Media: Part 2: Citric Acid Production and Circular-Oriented Valorization of Glucose-Enriched Olive Mill Wastewaters Using Novel Yarrowia lipolytica Strains

“…The effective bioconversion of renewable feedstocks into CA has been achieved with wild-type, recombinant or engineered strains of Y. lipolytica [ 12 , 40 , 43 ]. According to the literature, CA production by wild-type strains of Y. lipolytica can be, in rare cases, in concentrations up to 100 g/L CA, whereas mutant strains may generate more than 100 g/L, while maximum CA concentrations up to 160 g/L have been indicated in some reports in the literature [ 5 , 12 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ].…”

Engineering the oleaginous yeast Yarrowia lipolytica to produce nutraceuticals: From metabolic design to industrial applications

“…Moreover, the C/N ratio in the medium also has a significant impact on citrate production. Giacomobono et al (2022) explored the effects of the C/N ratio on citrate production from crude glycerol using the response surface method and achieved a maximal conversion yield of 0.249 g/g when the C/N ratio was 141. Additionally, the isocitrate dehydrogenase could convert citrate to isocitrate, which is regulated by the intracellular AMP level.…”