The Studies On Citrus Molasses And Alcohol Production From Citrus Processing Residues

This paper focused on extracting molasses and producing fuel ethanol by utilization of citrus processing-residues. This study involved in extraction of citrus molasses, analysis of molasses composition, screening of strains, optimization of fermentation conditions, distillation of condensed fermented mash and preparation of dehydrated alcohol in order to exploring feasibility of industrialized fuel alcohol manufacture..The citrus wastes were mixed fully with 0.3% quicklime (weight bass), recation completely by standing for 20 minutes, the mixture was pressing by presser and filtered by finisher to obtain filtrate. Standing was performed for 12 hours and the oils over filtrate were removed by siphonic process. The filtrate was concentrated into 40°Brix molasses by vacuum rotary evaporation.The citrus pulps excreted from finisher were washed for 5 times to recover all sugar. The pulp wash could either be fermented directly or diluted with citrus molasses before fermentation. It could also be concentrated and mixed with citrus molasses for fermentation and alcohol productionThe results of composition analysis of citrus molasses and pulp wash were given as follow that the soluble solids content of the citrus press juice was 11.8°Brix, reducing sugar 5.57g/100ml, total sugar 9.28g/100ml, oils 0.756%(by weight).While molasses was 40°Brix, the reducing sugar 15g/100ml, total sugar 34g/100ml and oils 0.05%(by weight).The contents of pectin in pulp wash and molasses were 0.474% and 0.653% respectively.There was not significant influence on growth of Saccharomyces cerevisiae if content of the oils in dilution solution of molasses was lower than 0.03%.However, when the content exceeds 0.04%, the growth of Saccharomyces cerevisiae was significantly affected by the oils and the lag phase was extended. In our study, the content of the oils in dilution solution of molasses was lower than 0.04% and fermentation was not influenced obviously.Through comparative assay about 6 strains of X1, X2, X3, X4, X5 and X6, it indicated that X4 was the optimal strain for fermentation resulting either the alcohol yield or the suitability in citrus molasses culture medium. The yields of ethanol from directly waste sugar solution and citrus molasses fermented by X4 were 20g/L and 72g/L respectively.In single factor experiment, the superior conditions could be 25°Brix medium of molasses, 1.8 g/L, (NH₄)₂SO₄ , 0.6g/L KH₂PO₄ and 0.6g/L MgSO₄,pH 5.0 and inoculums size was 3×10⁷individual/ml, and ethanol yield was 82.4 g/L.The optimal technological conditions determined by orthogonal experiment were initial pH 5.0, inoculums size 3×10⁷individual/ml under 30℃. The maximum alcohol yield was got.Experiments In 15L fermentor based on single factor and an orthogonal experiment was carried out fermentation curves were similar with those from shake flasks except a shorter lag phase. It could be confiremed that fermentation ability of this strain both in fermentor and shake flasks were no difference. It also manifested the stabilized fermented ability of this strain proved by amplified experiment after shake flasks.At last, 95% alcohol was obtained after atmospheric distillation 3 times and vacuum distillation once.The citrus molasses were made from citrus processing residues which was no cost. Through economical analysis, citrus molasses alcohol has competitive advantage comparing with corn alcohol and sweet sorghum stem alcohol. Industrial manufacture would be feasible if there were sufficient citrus processing residues and thus citrus molasses would be a kind of potentially biological energy sources.In a word, it was concluded that after proper processing, citrus molasses could be obtained from the citrus residues and then fermented into alcohol. It was also valuable to make comprehansive utilization of the citrus residues with a strong competitive strength to produce fuel ethanol.