ISOLATION AND IDENTIFICATION OF YEAST STRAINS FROM SUGARCANE MOLASSES, DATES AND FIGS FOR ETHANOL PRODUCTION UNDER CONDITIONS SIMULATING ALGAL HYDROLYSATE

International audienceYeast strains were isolated from sugar cane molasses (S1), dates (S2) and figs (S3) and the ethanol production was evaluated in batch condition. A comparison was made with the yeast Saccharomyces cerevisiae. The strains showed tolerant characteristics to stressful conditions like salinity and ethanol. The isolated strains produced ethanol; at 20 h of fermentation ethanol yields were 0.38-0.39 g.g-1 , and the productivities were almost 0.58 g.L-1. S. cerevisiae and S1 tolerated up to 14% (v/v) of ethanol; while interestingly the isolates S2 and S3 were highly tolerant, up to 20% (v/v) ethanol. Thus, S2 and S3 could serve as potential strains for ethanol fermentation, with 0.27 and 0.29 g.g-1 yield of ethanol in the presence of 1.37 mol.L-1 NaCl. These values were higher than the value obtained using the yeast of reference and S1 (0.16 g.g-1). Co-cultures of S2 and S3 enhanced the ethanol production, increasing the yield of ethanol by 12.5% compared with the single culture. The strains were identified as species S.cerevisiae, and S2 and S3 were very similar. For an application in the valorization of biomass such as green macro-algae, some assays were done on a synthetic model medium of hydrolysate of macro-algae and the strains S2 and S3 demonstrated excellent fermentative performances

Experimental study and kinetic modelling of bioethanol production from industrial potato waste

International audienceThe potato wastes constitute a major environmental concern due to their significant production in the potato processing industry. Due to their high organic content, this waste can constitute a very interesting Algerian resource for biofuel production. The objective of this study is the energy recovery of an industrial agro-food waste to produce bioethanol. This waste is a solid residue of chips manufacturing and mainly consists of potato starch. The conversion of this biomass was achieved using a chemical pretreatment with hydrochloric acid. The acid hydrolysis of potato starch with a ratio of material to acid solution of 1:2 (w/v) was enough to liberate a high amount of fermentable reducing sugar (159.3 g/l) contained in the potato waste. The hydrolysate obtained at the end was fermented using Saccharomyces cerevisiae yeast under the following conditions (pH 5, 30 degrees C, 100 rpm). The maximum yield of bioethanol (54.12 g/l) was achieved after 116 h. Thus, operating conditions used for the sugar fermentation were favorable and did not exhibit any sort of process inhibition. The Gompertz model was applied to experimental data, and kinetic fermentation parameters such as maximum ethanol concentration (P-m = 49.81 g/l), production rate (r(pm) = 0.87 g/(l h)), and lag phase (t(L) = 5.29 h) were accurately estimated. Those parameters can be used to investigate the economical feasibility for such industry. The results demonstrate that potato starch (by-product of the potato industry) has a great potential for bioethanol production