Production of Omega-3 Fatty Acids from the Microalga Crypthecodinium cohnii by Utilizing Both Pentose and Hexose Sugars from Agricultural Residues

Abstract

The core objective of this work was to take advantage of the unexploited wheat straw biomass, currently considered as a broadly available waste stream from the Greek agricultural sector, towards the integrated valorization of sugar streams for the microbial production of polyunsaturated omega-3 fatty acids (PUFAs). The OxiOrganosolv pretreatment process was applied using acetone and ethanol as organic solvents without any additional catalyst. The results proved that both cellulose-rich solid pulp and hemicellulosic oligosaccharides-rich aqueous liquid fraction after pretreatment can be efficiently hydrolyzed enzymatically, thus resulting in high yields of fermentable monosaccharides. The latter were supplied as carbon sources to the heterotrophic microalga Crypthecodinium cohnii for the production of PUFAs, more specifically docosahexaenoic acid (DHA). The solid fractions consisted mainly of hexose sugars and led to higher DHA productivity than their pentose-rich liquid counterparts, which can be attributed to the different carbon source and C/N ratio in the two streams. The best performance was obtained with the solid pulp pretreated with ethanol at 160 °C for 120 min and an O2 pressure of 16 bar. The total fatty acids content reached 70.3 wt% of dried cell biomass, of which 32.2% was DHA. The total DHA produced was 7.1 mg per g of untreated wheat straw biomass.

Single Cell Protein Production through Multi Food-Waste Substrate Fermentation

“…From a chemical point of view, food waste is mainly composed by carbohydrate polymers such as starch, proteins, lipids, cellulose, and other microelements [7][8][9][10]. Due to this composition, it is classified as a low cost, high potency second generation feedstock [1], and usable as a substrate for microbial fermentation for bioconversion into value added products, such as enzymes, feed additives, biofuels, animal feeds as well as other useful chemicals or products, food grade pigments, and single cell protein (SCP), enhancing food security and environmentally sustainable development [11][12][13][14][15][16][17][18][19][20][21].…”

Characterization of a Dual Cellulolytic/Xylanolytic AA9 Lytic Polysaccharide Monooxygenase from Thermothelomyces thermophilus and its Utilization Toward Nanocellulose Production in a Multi-Step Bioprocess

“…7,14,24,58 OxiOrganosolv pretreatment with acetone as organic solvent and oxygen gas was employed as a pretreatment step since it has been shown to efficiently remove lignin and enable the efficient fractionation of not only hardwood biomass such as beechwood but also softwoods and agricultural biomass. 23,59 The application of an initial pretreatment step is of pivotal importance since enzymatic hydrolysis of raw material suffers from low yields due to the recalcitrant grid of lignocellulosic biomass. In addition, pretreatment with acetone has been shown to promote cellulose fibril swelling, while maintaining crystallinity.…”

Recycling Fermentation Strategy for Waste Cellular Residues in the Production of Polyunsaturated Fatty Acids

“…Among the cost factors, the fermentation medium plays a particularly significant role [10][11][12]. As a result, inexpensive raw materials have been explored as substitutes for traditional costly components like glucose and yeast extract [7,[13][14][15].…”