Optimization of enzymatic hydrolysis of cellulosic fraction obtained from stranded driftwood feedstocks for lipid production by Solicoccozyma terricola

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Stranded driftwood feedstocks (SD) were steam exploded and hydrolyzed.

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The enzymatic hydrolysis was optimized using a multivariate approach (RSM).

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The conversion of carbohydrates into lipids by S. terricola was high (Y_L = 25.26%).

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The fatty acid profile achieved was similar to that reported for palm oil.

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SD feedstocks resulted a cheap C-source for biofuels and biochemicals production.

Stranded driftwood feedstocks may represent, after pretreatment with steam explosion and enzymatic hydrolysis, a cheap C-source for producing biochemicals and biofuels using oleaginous yeasts. The hydrolysis was optimized using a response surface methodology (RSM). The solid loading (SL) and the dosage of enzyme cocktail (ED) were variated following a central composite design (CCD) aimed at optimizing the conversion of carbohydrates into lipids (Y_L) by the yeast Solicoccozyma terricola DBVPG 5870.

A second-order polynomial equation was computed for describing the effect of ED and SL on Y_L.

The best combination (ED = 3.10%; SL = 22.07%) for releasing the optimal concentration of carbohydrates which gave the highest predicted Y_L (27.32%) was then validated by a new hydrolysis. The resulting value of Y_L (25.26%) was close to the theoretical maximum value.

Interestingly, fatty acid profile achieved under the optimized conditions was similar to that reported for palm oil.

Yeast lipids from cardoon stalks, stranded driftwood and olive tree pruning residues as possible extra sources of oils for producing biofuels and biochemicals

BACKGROUND

Some lignocellulosic biomass feedstocks occur in Mediterranean Countries. They are still largely unexploited and cause considerable problems due to the lack of cost-effective harvesting, storage and disposal technologies. Recent studies found that some basidiomycetous yeasts are able to accumulate high amount of intracellular lipids for biorefinery processes (i.e., biofuels and biochemicals). Accordingly, the above biomass feedstocks could be used as carbon sources (after their pre-treatment and hydrolysis) for lipid accumulation by oleaginous yeasts.

RESULTS

Cardoon stalks, stranded driftwood and olive tree pruning residues were pre-treated with steam-explosion and enzymatic hydrolysis for releasing free mono- and oligosaccharides. Lipid accumulation tests were performed at two temperatures (20 and 25 °C) using Leucosporidium creatinivorum DBVPG 4794, Naganishia adeliensis DBVPG 5195 and Solicoccozyma terricola DBVPG 5870. S. terricola grown on cardoon stalks at 20 °C exhibited the highest lipid production (13.20 g/l), a lipid yield (28.95%) close to the maximum theoretical value and a lipid composition similar to that found in palm oil. On the contrary, N. adeliensis grown on stranded driftwood and olive tree pruning residues exhibited a lipid composition similar to those of olive and almonds oils. A predictive evaluation of the physical properties of the potential biodiesel obtainable by lipids produced by tested yeast strains has been reported and discussed.

CONCLUSIONS

Lipids produced by some basidiomycetous yeasts grown on Mediterranean lignocellulosic biomass feedstocks could be used as supplementary sources of oils for producing biofuels and biochemicals.