Lipids from yeasts and fungi: physiology, production and analytical considerations

Abstract

The last years there has been a significant rise in the number of publications in the international literature that deal with the production of lipids by microbial sources (the 'single cell oils; SCOs' that are produced by the so-called 'oleaginous' micro-organisms). In the first part of the present review article, a general overview of the oleaginous micro-organisms (mostly yeasts, algae and fungi) and their potential upon the production of SCOs is presented. Thereafter, physiological and kinetic events related with the production of, mostly, yeast and fungal lipids when sugars and related substrates like polysaccharides, glycerol, etc. (the de novo lipid accumulation process) or hydrophobic substrates like oils and fats (the ex novo lipid accumulation process) were employed as microbial carbon sources, are presented and critically discussed. Considerations related with the degradation of storage lipid that had been previously accumulated inside the cells, are also presented. The interplay of the synthesis of yeast and fungal lipids with other intracellular (i.e. endopolysaccharides) or extracellular (i.e. citric acid) secondary metabolites synthesized is also presented. Finally, aspects related with the lipid extraction and lipidome analysis of the oleaginous micro-organisms are presented and critically discussed.

Waste fat biodegradation and biomodification by Yarrowia lipolytica and a bacterial consortium composed of Bacillus spp. and Pseudomonas putida

“…In general, in our study, the values of Y X/S obtained for both fats were very satisfactory when compared with the average value (ca 1.0 g/g) reported in the literature for Y. lipolytica [5,[18][19][20][44][45][46] or for other microorganisms capable of growth on several fatty materials employed as substrates (i.e. that promote the synthesis of organic acids or the de novo synthesis of microbial lipid [7,15]), the current Y. lipolytica strain produced noticeable quantities of citric acid (up to ca 58 g/L) [29]. [14,29,47].…”

“…The profile of the cellular lipids of Y. lipolytica resembled the FA composition of the medium. Also in the case of the bacterial consortium, the same trend was observed intracellularly, suggesting that 9C18:1 was rapidly incorporated by the bacterial cells, and was equally rapidly assimilated through the β-oxidation process for energy production [7]. A similar response was observed for the bacterial consortium that preferentially degraded 9C18:1 (Table 4).…”

“…Ota and Kushida [43] reported a yield of 0.88 g/g for Candida sp. Extra-cellular and intra-cellular fatty acids (%, w/w) when the bacterial consortium (BFL-CP1) was grown on waste cooked butter and olive oil saturated FAs, that, as stressed are not easily assimilated by several types of microorganisms [7,15]. These results again demonstrate the challenge of various microbial strains belonging to Y. lipolytica to degrade "hard" fats, composed mainly of Table 4.…”

“…The initial concentration of the oil was lower than in our study, namely ß2 g/L, and they observed a 93.3% w/w removal of salad oil and 85.1% w/w removal of grease under optimum conditions. Thereafter, the various FAs, that had previously been released from TAG structures through lipase-catalyzed hydrolysis, or exist as initial substrates (in several cases fatty by-products composed of free FAs have been employed as microbial substrates [11,12,20]), are incorporated inside the microbial cells or mycelia with different incorporation rates depending on their structure and the sufficiency of cell membrane in specific FA carriers [5,7,11,15,16]. Tzirita and Quilty [39] have reported 94% biodegradation of butter (S 0 = 7.5 g/L) and 92% of olive oil (S 0 = 8 g/L) in an enriched medium by the fungus Mucor circinelloides after 13 days of incubation.…”

“…This organism can use triacylglycerols (TAGs) as a sole carbon source which are hydrolyzed to FAs and glycerol. The released FAs will be further incorporated inside the yeast cells through a process that is not random [20] and will either be metabolized through the β-oxidation pathway, or will be stored in the lipid reserves unaltered or following reactions of elongation or unsaturation [5,7,15,16]. Besides regiospecificity, microbial lipases may also exhibit FA specificity, recognizing specific aliphatic chains according to their number of carbon atoms and double bonds [16][17][18][19].…”