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

Giorgia Tasselli; Sara Filippucci; Silvia D'Antonio; Gianluca Cavalaglio; Benedetta Turchetti; Franco Cotana; Pietro Buzzini

doi:10.1016/j.btre.2019.e00367

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

Biotechnol Rep (Amst). 2019 Aug 7:24:e00367. doi: 10.1016/j.btre.2019.e00367. eCollection 2019 Dec.

Authors

Giorgia Tasselli^{1

2}, Sara Filippucci¹, Silvia D'Antonio², Gianluca Cavalaglio^{2

3}, Benedetta Turchetti¹, Franco Cotana^{2

3}, Pietro Buzzini^{1

2}

Affiliations

¹ Department of Agricultural, Food and Environmental Sciences, Industrial Yeasts Collection DBVPG, University of Perugia, Italy.
² CIRIAF - Biomass Research Centre, University of Perugia, Italy.
³ Department of Engineering, University of Perugia, Italy.

Abstract

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.

Keywords: A600, absorbance at 600 nm; ANOVA, analysis of variance; C/N, carbon/nitrogen; C10:0, capric acid (decanoic acid); C12:0, lauric acid (dodecanoic acid); C14:0, myristic acid (tetradecanoic acid); C16:0, palmitic acid (hexadecanoic acid); C18:0, stearic acid (octadecanoic acid); C20:0, arachic acid (eicosanoic acid); C22:0, behenic acid (docosanoic acid); C24:0, lignoceric acid (tetracosanoic acid); C5, carbohydrates with five carbon atoms; C6, carbohydrates with six carbon atoms; C8:0, caprylic acid (octanoic acid); CBU, cellobiase unit; CCD, Central Composite Design; DW, dry weight; ED, enzyme dosage; Enzymatic hydrolysis; Eq, equation; F.A.M.E., fatty acid methyl ester; FA, fatty acid; FPU, filterpaper unit; GC, Gas Chromatography; GC-FID, Gas Chromatography – Flame Ionization Detector; HLF, hydrolyzed liquid fraction; HPLC, high performance liquid chromatography; LF, liquid fraction; NREL, National Renewable Energy Laboratory; PL, total lipid production; PL/DW, % of total intracellular lipid on cellbiomass; PL/d, lipid production per day; RI, refractive index; RSM, response surface methodology; Response surface methodology; Rpm, revolutions per minute; SD, stranded driftwood; SE, steam explosion; SFA, saturated fatty acid; SL, solid loading; Solicoccozyma terricola; Stranded driftwood feedstocks; TAGs, Tryacylglicerols; UFA, unsaturated fatty acid; UI, unsaturation index; WIS, water insoluble substrate; XG, Xilose and Galactose; YL, lipid yied; YPD, Yeast Extract Peptone Dextrose; Yeast biochemicals and biofuels; Yoleic, oleic acid yield; g, gravity force; h, hours; min, minutes; p, p-value; v/v, concentration in volume/volume percent; Δ13C22:1, erucic acid [(13Z)-docos-13-enoic acid]; Δ9,12,15C18:3, linolenic acid [(9Z,12Z,15Z)-9,12,15-octadecatrienoic acid]; Δ9,12C18:2, linoleic acid [(9Z,12Z)-9,12-octadecadienoic acid]; Δ9C16:1, palmitoleic acid [(9Z)-hexadec-9-enoic acid]; Δ9C18:1, oleic acid [(9E9Z)-octadec-9-enoic acid].