Dynamic model of temperature impact on cell viability and major product formation during fed-batch and continuous ethanolic fermentation in Saccharomyces cerevisiae
Université de Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France. Bioresource Technology
(Impact Factor: 4.49).
04/2012; 117:242-50. DOI: 10.1016/j.biortech.2012.04.013
The impact of the temperature on an industrial yeast strain was investigated in very high ethanol performance fermentation fed-batch process within the range of 30-47 °C. As previously observed with a lab strain, decoupling between growth and glycerol formation occurred at temperature of 36 °C and higher. A dynamic model was proposed to describe the impact of the temperature on the total and viable biomass, ethanol and glycerol production. The model validation was implemented with experimental data sets from independent cultures under different temperatures, temperature variation profiles and cultivation modes. The proposed model fitted accurately the dynamic evolutions for products and biomass concentrations over a wide range of temperature profiles. R2 values were above 0.96 for ethanol and glycerol in most experiments. The best results were obtained at 37 °C in fed-batch and chemostat cultures. This dynamic model could be further used for optimizing and monitoring the ethanol fermentation at larger scale.
Available from: Yan Wang
- "Biofuel, a renewable and clean energy source, is considered as an effective substitute for petroleum-based products . Among various types of biofuels, bio-ethanol is most popular and has a great potential to replace the motor fuels    . In order to obtain the ethanol product with a high purity from the commercial fermentation process, efficient purification process is needed , which actually accounts for 60–80% in the overall cost of alcohol production in the current situation. "
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ABSTRACT: In this work, two novel poly(vinyl alcohol) (PVA)/organosilica hybrid membranes are developed via the sol-gel process, with phenyltriethoxysilane (PTES) and diethoxydiphenylsilane (DEDPS) as crosslinkers and organosilica precursors, and employed for ethanol dehydration via pervaporation. Effects of organosilane type on the membrane morphology, physicochemical properties and pervaporation performance of the as-fabricated membranes are studied. In addition, the effects of the organosilane loading and the thermal treatment temperature on the physicochemical properties and pervaporation performance of the membrane are explored systematically. Various characterization techniques (FT-IR, TGA, SEM, etc) are employed to illuminate physicochemical changes of membranes. The optimal pervaporation performance of PVA-PTES hybrid membrane with 0.4mmol/g PTES loading and thermally treated at 80°C has a flux of 145g/m2h and a separation factor of 1026 for the pervaporation dehydration of 85% ethanol aqueous solution at 40°C.
Available from: Meisam Tabatabaei
- "In other words, the concentrations of ethanol and xylitol reached 55 g/L (yield of 0.70 g/g) and 31 g/L (yield of 0.78 g/g) at the 150th hour, respectively, which were significantly higher than those obtained in the batch single and co-culture systems (Fig. 6). Numerous studies have previously emphasized on the advantages of continuous production of ethanol and therefore strived to produce ethanol from different biomass by using different continuous fermentation systems, such as cell recycling or/and in situ ethanol removal (e.g., Zhang et al. 2005; Chen et al. 2012; Ntihuga et al. 2012), modeling or/ and optimizing different fermentation parameters (e.g., Amillastre et al. 2012; Khongsay et al. 2012; Sharma and Rangaiah 2012), and using different fermentor designs and fermentation techniques (e.g., Ding et al. 2011; Kundiyana et al. 2011; Moon et al. 2012). Our results also proved the great advantage of continuous co-production of ethanol and xylitol from rice straw feedstock over batch single production. "
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ABSTRACT: The present study was set to develop a robust and economic biorefinery process for continuous co-production of ethanol and xylitol from rice straw in a membrane bioreactor. Acid pretreatment, enzymatic hydrolysis, detoxification, yeast strains selection, single and co-culture batch fermentation, and finally continuous co-fermentation were optimized. The combination of diluted acid pretreatment (3.5 %) and enzymatic conversion (1:10 enzyme (63 floating-point unit (FPU)/mL)/biomass ratio) resulted in the maximum sugar yield (81 % conversion). By concentrating the hydrolysates, sugars level increased by threefold while that of furfural reduced by 50 % (0.56 to 0.28 g/L). Combined application of active carbon and resin led to complete removal of furfural, hydroxyl methyl furfural, and acetic acid. The strains Saccharomyces cerevisiae NCIM 3090 with 66.4 g/L ethanol production and Candida tropicalis NCIM 3119 with 9.9 g/L xylitol production were selected. The maximum concentrations of ethanol and xylitol in the single cultures were recorded at 31.5 g/L (0.42 g/g yield) and 26.5 g/L (0.58 g/g yield), respectively. In the batch co-culture system, the ethanol and xylitol productions were 33.4 g/L (0.44 g/g yield) and 25.1 g/L (0.55 g/g yield), respectively. The maximum ethanol and xylitol volumetric productivity values in the batch co-culture system were 65 and 58 % after 25 and 60 h, but were improved in the continuous co-culture mode and reached 80 % (55 g/L) and 68 % (31 g/L) at the dilution rate of 0.03 L per hour, respectively. Hence, the continuous co-production strategy developed in this study could be recommended for producing value-added products from this hugely generated lignocellulosic waste.
Available from: sciencedirect.com
- "In this context, ethanol has a prominent role, its worldwide production indicators having risen from control (Ngwenya et al., 2012). Indeed the effects of inadequate temperature conditions include reduction of fermentation yield, changes in cell viability and decrease of yeast tolerance to ethanol (Amillastre et al., 2012). Besides, fermentation under suboptimal temperatures can favor wild microorganism which will compete with S. cerevisiae for substrate. "
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ABSTRACT: In this study it was proposed the application of a fuzzy-PI controller in tandem with a split range control strategy to regulate the temperature inside a fermentation vat. Simulations were carried out using different configurations of fuzzy controllers and split range combinations for regulatory control. The performance of these control systems were compared using conventional integral of error criteria, the demand of utilities and the control effort. The proposed control system proved able to adequately regulate the temperature in all the tests. Besides, considering a similar ITAE index and using the energetically most efficient split range configuration, fuzzy-PI controller provided a reduction of approximately 84.5% in the control effort and of 6.75% in total demand of utilities by comparison to a conventional PI controller.
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