Biotechnological Conversions of Mizithra Second Cheese Whey by Wild-Type Non-Conventional Yeast Strains: Production of Yeast Cell Biomass, Single-Cell Oil and Polysaccharides

Abstract

The cultivation of oleaginous yeasts on various agro-industrial residues and the subsequent production of microbial lipids (single-cell oils), which can be used as starting materials for the synthesis of both “second generation” biodiesel and various types of oleochemicals, is considered as one of the most important approaches of the Industrial Biotechnology, in terms of circular economy and green and sustainable development. In this study, seven wild-type non-conventional yeast strains were evaluated for their growth on a semi-defined medium with cheese whey lactose as a sole carbon source. Five of these strains were further batch-cultivated into the complex substrate that contained second cheese whey, which is the main by-product of Mizithra whey cheese manufacture, after centrifugation and filtration without any extra mineral salts, carbon, or nitrogen source addition. All these five strains grown in second cheese whey produced mainly yeast biomass and to lesser extent microbial lipids and other interesting metabolites, such as polysaccharides. The strain Cryptococcus curvatus ATCC 20509 produced the highest total dry weight (TDW) amount (22.4 g/L), that contained 3.4 g/L of intra-cellular lipids, followed by C. curvatus NRRL Y-1511, which produced 20.6 g/L of TDW and 3.2 g/L lipids. A novel, non-previously systematically studied strain, namely Papiliotrema laurentii NRRL Y-2536, produced significant quantities of TDW (22.0 g/L) and, interestingly, secreted quantities of exopolysaccharides. Fed-batch shake-flask cultivation of C. curvatus ATCC 20509 in pretreated second cheese whey, pulse-supplemented with condensed cheese whey-derived lactose, led to the significant TDW quantity of 38.1 g/L that contained c. 57% w/w of total lipids (lipids at a concentration 21.7 g/L were produced). Cellular lipids of all microorganisms, mainly stored as triacylglycerols, contained in variable quantities the fatty acids Δ9C18:1, C16:0, Δ9,12C18:2 and C18:0, constituting perfect candidates for the synthesis of “second generation” biodiesel.

Screening of New Industrially Important Bacterial Strains for 1,3-Propanediol, 2,3-Butanediol and Ethanol Production through Biodiesel-Derived Glycerol Fermentations

“…Analyses performed by ASG Analytik-Service AG (Neusäss, Germany) indicated that the glycerol content was 74.9%, the water content was 11.8%, the ash content was 3.4%, the methanol content was 2.05% and the non-glycerol organic matter content was 9.9%. The initial pH value was set at 7.2 ± 0.1, and pH adjustment, when necessary, was performed as in Vasilakis et al [ 22 ]. The main culture was inoculated after sterilization (121 °C, 20 min); the strains were derived from the pre-culture (ranging between 0.5 and 10% of the working fermentation volume) when the cell growth was in the exponential phase.…”

Sheep’s Second Cheese Whey Edible Coatings with Oregano and Clary Sage Essential Oils Used as Sustainable Packaging Material in Cheese

“…Some manuscripts are related to the use of SCW as a biotechnological substrate for probiotic or starter cultures [ 18 , 19 , 20 ]. Others refer to its potential to produce biofuel products [ 21 , 22 , 23 ]. The use of SCW to produce fermented drinks or as an ingredient in food formulations, was also evaluated [ 3 , 24 , 25 , 26 , 27 , 28 ].…”

Exploring the Potential of Halloumi Second Cheese Whey for the Production of Lactic Acid Cultures for the Dairy Industry

“…Worldwide, various strategies have been adopted attempting to manage SCW due to the restrictions and the demanding economic costs of its disposal. Although not so widely investigated as cheese whey [3,4], a literature review related to SCW revealed it is mainly exploited as a fermentation medium for the sustainable generation of added-value products, including biofuels [5], eco-friendly bioplastics (e.g., polyhydroxyalkanoates) [6,7] and polysaccharides, as well as for biomass production [8,9]. In addition, SCW seems to offer a promising alternative source for the development of innovative food products such as probiotic drinks [5] and vinegar [6].…”