A waste-free, microbial oil centered cyclic bio-refinery approach based on flexible macroalgae biomass

Lipid production through the single-step microwave hydrolysis of macroalgae using the oleaginous yeast Metschnikowia pulcherrima

“…Although following microwave processing M. pulcherrima could degrade macroalgae polysaccharides, a substantial amount remained in the fermentation broth, hindering higher biomass conversion ratios. To fully valorise the available polysaccharides, additional processing such as extraction or breakdown [1,17] may be considered. As non-sterility and the absence of supplementary enzymes potentially make the proposed process particularly low-cost, the benefit of those additional treatment must be economically assessed.…”

“…The obtained lipid concentration of 2.6 g L −1 for M. pulcherrima grown on macroalgae hydrolysate is superior to those on hydrolysates of wheat straw (1.2 g L ), of which all were hydrolysed through microwave hydrothermal pretreatment [20]. In comparison with other (oleaginous) yeasts, the results place M. pulcherrima as highly suitable for valorisation of macroalgae hydrolysates: ethanol yields through fermentation of Saccharomyces cerevisiae on A. nodosum microwave hydrolysate (0.02 g g −1 macroalgae), and also lipid yields with respect to monosaccharides with R. toruloides on Laminaria residue acid + enzyme hydrolysate (0.16 g g −1 total reducing sugars) [14] and Cutaneotrichosporon oleaginosus on L. digitata (March/June) enzyme hydrolysate (0.32 g g −1 monosaccharides) [17] were lower. However, higher overall valorisation of macroalgae to lipids has been reported (0.21 g g −1 macroalgae) [17], mostly contingent on the different harvesting time and nearly full hydrolysis of polyinto monosaccharides (<95% w/w) through the application of 72 h enzymatic pretreatment (monosaccharide yield 650 mg g −1 macroalgae).…”

“…In comparison with other (oleaginous) yeasts, the results place M. pulcherrima as highly suitable for valorisation of macroalgae hydrolysates: ethanol yields through fermentation of Saccharomyces cerevisiae on A. nodosum microwave hydrolysate (0.02 g g −1 macroalgae), and also lipid yields with respect to monosaccharides with R. toruloides on Laminaria residue acid + enzyme hydrolysate (0.16 g g −1 total reducing sugars) [14] and Cutaneotrichosporon oleaginosus on L. digitata (March/June) enzyme hydrolysate (0.32 g g −1 monosaccharides) [17] were lower. However, higher overall valorisation of macroalgae to lipids has been reported (0.21 g g −1 macroalgae) [17], mostly contingent on the different harvesting time and nearly full hydrolysis of polyinto monosaccharides (<95% w/w) through the application of 72 h enzymatic pretreatment (monosaccharide yield 650 mg g −1 macroalgae). Whilst the time of this hydrolysis method is considerable higher, and the treatment more cost-intensive these results emphasize that further work is necessary to optimise microwave hydrothermal pretreatment of macroalgae, but also enhance metabolism of polysaccharides in M. pulcherrima, prior to moving this promising process beyond laboratory scale.…”

“…Current research has developed techniques to enhance macroalgae valorisation through collaterally extracting proteins [1] and/or utilising other available saccharides, for instance through purification [12] or microbial processing [13][14][15][16][17][18]. Whilst the high carbohydrate, sulphur and nitrogen content make macroalgae a promising feedstock for microbial fermentation within a biorefinery setting, pretreatment and fermentation within such as process should be cost efficient and sustainable, utilising a microbe with versatile characteristics and ideally yield high-value products to enhance the feasibility of such a process.…”

“…With macroalgae (potentially) embodying these characteristics [14], strong cases emphasising the aforementioned advantages over lignocellulosic biomass are made for utilisation in renewable energy production [2,3]. Whilst for these reasons there are a few reports of producing microbial lipids from macroalgae recently [13,14,17,18], coupling low-energy microwave depolymerisation with M. pulcherrima offers additional benefits for a potentially more economic route to microbial lipid production. Investigating the suitability of this novel system for development beyond laboratory scale, this study goes beyond previous studies through extensively considering the impact of species on the process.…”