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Orange peel waste (OPW), the primary byproduct of the juice extraction process, is annually generated in massive amounts (21 Mton), and its aqueous extraction in biorefining operations yields a liquid fraction, referred to as orange peel extract (OPE). Although OPE contains significant amounts of easily assimilable carbohydrates, such as fructose, glucose, and sucrose, no investigations have been conducted yet to assess its possible use in biodiesel production by oleaginous yeasts. Consequently, the objective of the present study was to assess whether OPE might act as the basis of a liquid medium for microbial lipid production. A screening conducted with 18 strains of oleaginous yeasts in shaken flask on the OPE-based medium showed that Rhodosporidium toruloides NRRL 1091 and Cryptococcus laurentii UCD 68-201 gave the best results in terms of lipid production (5.8 and 4.5 g L−1, respectively) and accumulation (77 and 47% on a dry matter basis, respectively). The subsequent scale transfer of the process to a 3-L STR operated in batch mode halved the time required to reach the lipid peak with the ensuing increase in volumetric productivities in R. toruloides NRRL 1091 (3646 mg L−1 day−1) and C. laurentii UCD 68-201 (2970.7 mg L−1 day−1). The biodiesel yields from the lipids of the former and the latter strain were 36.9 and 31.9%, respectively. Based on multivariate analysis of fatty acid methyl ester compositions, the lipids from the former and the latter strain were highly resembling those of Jatropha and palm oils, two commonly used feedstocks for biodiesel manufacturing. [ABSTRACT FROM AUTHOR]

Microbial oils are regarded as a sustainable alternative to vegetable oils for biodiesel manufacturing. However, in order to develop a cost-effective process, high-lipid producer microorganisms should be combined with low-cost renewable growth substrates. For this reason, the objective of the present study was to assess comparatively the oil-producing performance of 9 oleaginous fungi belonging to the Aspergillus, Mucor, Mortierella and Cunninghamella genera on three relevant and widespread waste, such as glycerol, orange peel extract (OPE) and ricotta cheese whey (RCW). This screening was performed at the shaken flask level and, among the strains under study, Mortierella isabellina NRRL 1757 turned out to be the most efficient and versatile and its lipid profile was found to be highly compatible with biodiesel production. Process transfer of M. isabellina lipid production to the lab-scale Stirred Tank Reactor on all the three waste-based media, was shown to be feasible, achieving a lipid productivity of 0.46, 1.24 and 0.91 g/(L d) on glycerol, OPE and RCW, respectively. Noteworthy, the fatty acid analysis of the oils produced, confirmed their suitability for biodiesel manufacturing, exhibiting a high similarity to palm and Jatropha oils commonly used as feedstock for this production. [ABSTRACT FROM AUTHOR]

The increasing demand of plant oils for biodiesel production has highlighted the need for alternative strategies based either on non-food crops or agro-industrial wastes that do not compete with food and feed production. In this context, the combined use of wastewater and oleaginous microorganisms could be a valuable production option. Ricotta cheese whey (RCW), one of the major byproducts of the dairy industry, is produced in very high and steadily increasing amounts and, due to its high organic load, its disposal is cost-prohibitive. In the present study, in order to assess the adequacy of RCW as a growth medium for lipid production, 18 strains of oleaginous yeasts were investigated in shaken flask for their growth and lipid-producing capabilities on this substrate. Among them, Cryptococcus curvatus NRRL Y-1511 and Cryptococcus laurentii UCD 68-201 adequately grew therein producing substantial amounts of lipids (6.8 and 5.1 g L − 1 , respectively). A high similarity between the percent fatty acid methyl esters (FAME) composition of lipids from the former and the latter strain was found with a predominance of oleic acid (52.8 vs. 48.7%) and of total saturated fatty acids (37.9 vs. 40.8%). The subsequent scale transfer of the C. laurentii UCD 68-201 lipid production process on RCW to a 3-L STR led to significantly improved biomass and total lipid productions (14.4 and 9.9 g L − 1 , respectively) with the biodiesel yield amounting to 32.6%. Although the C. laurentii FAME profile was modified upon process transfer, it resembled that of the Jatropha oil, a well established feedstock for biodiesel production. In conclusion, C. laurentii UCD 68-201, for which there is very limited amount of available information, turned out to be a very promising candidate for biodiesel production and wide margins of process improvement might be envisaged. [ABSTRACT FROM AUTHOR]