Ethanol Production in Immobilized-Cell Bioreactors from Mixed Sugar Syrups and Enzymatic Hydrolysates of Steam-Exploded Biomass (original) (raw)
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Bioresource Technology, 2012
A system that incorporates a packed bed reactor for isomerization of xylose and a hollow fiber membrane fermentor (HFMF) for sugar fermentation by yeast was developed for facile recovery of the xylose isomerase enzyme pellets and reuse of the cartridge loaded with yeast. Fermentation of pre-isomerized poplar hydrolysate produced using ionic liquid pretreatment in HFMF resulted in ethanol yields equivalent to that of model sugar mixtures of xylose and glucose. By recirculating model sugar mixtures containing partially isomerized xylose through the packed bed and the HFMF connected in series, 39 g/l ethanol was produced within 10 h with 86.4% xylose utilization. The modular nature of this configuration has the potential for easy scale-up of the simultaneous isomerization and fermentation process without significant capital costs.
Ethanol fermentation in an immobilized cell reactor using Saccharomyces cerevisiae
Bioresource Technology, 2004
Fermentation of sugar by Saccharomyces cerevisiae, for production of ethanol in an immobilized cell reactor (ICR) was successfully carried out to improve the performance of the fermentation process. The fermentation set-up was comprised of a column packed with beads of immobilized cells. The immobilization of S. cerevisiae was simply performed by the enriched cells cultured media harvested at exponential growth phase. The fixed cell loaded ICR was carried out at initial stage of operation and the cell was entrapped by calcium alginate. The production of ethanol was steady after 24 h of operation. The concentration of ethanol was affected by the media flow rates and residence time distribution from 2 to 7 h. In addition, batch fermentation was carried out with 50 g/l glucose concentration. Subsequently, the ethanol productions and the reactor productivities of batch fermentation and immobilized cells were compared. In batch fermentation, sugar consumption and ethanol production obtained were 99.6% and 12.5% v/v after 27 h while in the ICR, 88.2% and 16.7% v/v were obtained with 6 h retention time. Nearly 5% ethanol production was achieved with high glucose concentration (150 g/l) at 6 h retention time. A yield of 38% was obtained with 150 g/l glucose. The yield was improved approximately 27% on ICR and a 24 h fermentation time was reduced to 7 h. The cell growth rate was based on the Monod rate equation. The kinetic constants (K s and l m ) of batch fermentation were 2.3 g/l and 0.35 g/l h, respectively. The maximum yield of biomass on substrate (Y X=S ) and the maximum yield of product on substrate (Y P=S ) in batch fermentations were 50.8% and 31.2% respectively. Productivity of the ICR were 1.3, 2.3, and 2.8 g/l h for 25, 35, 50 g/l of glucose concentration, respectively. The productivity of ethanol in batch fermentation with 50 g/l glucose was calculated as 0.29 g/l h. Maximum production of ethanol in ICR when compared to batch reactor has shown to increase approximately 10-fold. The performance of the two reactors was compared and a respective rate model was proposed. The present research has shown that high sugar concentration (150 g/l) in the ICR column was successfully converted to ethanol. The achieved results in ICR with high substrate concentration are promising for scale up operation. The proposed model can be used to design a lager scale ICR column for production of high ethanol concentration.
Journal of Biobased Materials and Bioenergy, 2012
To meet the ever increasing demand for energy and fuels, it is essential to produce renewable fuels such as bioethanol at low cost and in reduced time. In the present work, Saccharomyces cerevisiae was immobilized on a novel Pinewood chips (PC) support and the immobilized yeast was used in fermentation with an aim to increase bioethanol yield and productivity in single and mixed sugar fermentation. Different concentrations of glucose or xylose were used to see the effect on ethanol production from S. cerevisiae and P. stipitis, separately. With PC immobilized S. cerevisiae, ethanol yield of 0.44 g/g and productivity of 1.11 g/l · h were obtained for 200 g/l initial glucose concentration. This immobilized S. cerevisiae, was then used in co-culture along with free culture of Pichia stipitis for ethanol production from glucose-xylose sugar mixtures (1.5:1 ratio of glucose to xylose; average concentration 50.75 g/l) and compared with co-culture of free S. cerevisiae and free P. stipitis. Improvement in ethanol yield (0.47 g/g from 0.45 g/g in case of co-culture of free cells) and productivity (0.73 g/h.h from 0.45 g/l · h in case of co-culture of free cells) were obtained with co-culture of immobilized S. cerevisiae and free P. stipitis. Further, PC were treated with a sequential treatment of H 2 SO 4 followed by sodium sulphite and sodium chlorite and used to immobilize S. cerevisiae. Yeast immobilized on treated pine wood chips support (TP) was then used in co-culture with free P. stipitis and further improvement in ethanol yield (0.50 g/g) and productivity (0.80 g/l·h) were obtained for 50.8 g/l initial glucose-xylose mixture concentration. This work showed that this novel co-culture scheme of S. cerevisiae immobilized on pine wood chips and free P. stipitis can be used for efficient fermentation of mixed sugars to bioethanol.
This study presents ethanol production from molasses, dates and sugarcane syrup with sugar concentration of 35g/l in batch culture. Molasses (retention time, 24 h; initial sugar concentration, 100 g/l) gave highest yield of ethanol [conc., 45.5 g/l (theoretical yield 89%)] in a packed bed reactor loaded with immobilized Saccharomyces cerevisiae beads (mean diam, 3 mm). After 16 h of cultivation, free cells were harvested for immobilization. Entrapment method was used to encapsulate free cells using 2.5% sodium alginate solution, solidified in calcium chloride bath. Growth kinetic model for S. cerevisiae in batch culture and rate model for performance of immobilized cell reactor (ICR) were determined.
Ethanol Production from Cellulosic Biomass by Encapsulated Saccharomyces cerevisiae
2008
Unstable oil markets with rising environmental concerns have revived widespread interest in production of fuel ethanol from renewable materials. Cellulosic materials are abundant and prominent feedstocks for cheap ethanol production. However, due to recalcitrant structure of these materials, pretreatment is a prerequisite. Depending on the biomass, pretreatment and hydrolysis conditions, a number of degradation products and/or toxic components may be released that show strong inhibitory effects on the fermenting microorganisms. This thesis deals with application of encapsulation technology to ferment the highly toxic hydrolyzates without further pretreatment.
The production of ethanol by immobilized yeast cells
Biotechnology and Bioengineering, 1981
Sncchnromyces cerevisine cells were immobilized in calcium alginate beads for use in the continuous production of ethanol. Yeasts were grown in medium supplemented with ethanol to selectively screen for a culture which showed the greatest tolerance to ethanol inhibition. Yeast beads were produced from a yeast slurry containing 1.5% alginate (w/v) which was added as drops to a 0.05M CaC12 solution. To determine their optimum fermentation parameters, ethanol production using glucose as a substrate was monitored in batch systems at varying physiological conditions (temperature, pH, ethanol concentration), cell densities, and gel concentrations. The data obtained were compared to optimum free cell ethanol fermentation parameters. The immobilized yeast cells were examined in a packed-bed reactor system operated under optimized parameters derived from batch-immobilized yeast cell experiments. Ethanol production rates, as well as residual sugar concentrations were monitored at different feedstock flow rates.
2015
Continuous depletion of fossil fuel reserves and consequent rise in the price demands some alternative technology to meet the global requirement of energy. According to the report published in the United Nations conference on trade and development, the demand of ethanol in India was projected for the year 2016–2017 as 965.30 million litres. The main objective of the present study was ethanol fermentation from molasses using Saccharomyces cerevisiae (MTCC3090) strain for biomass substrate conversion from both free and immobilized [sodium alginate] cells were made and their ethanol yield and corresponding sugar consumption was compared. During first few batches ethanol fermentation using immobilized cells was less in comparison to fermentation using free yeast cells, but if reused the immobilized cells for subsequent batches it showed gradual increase in sugar consumption and ethanol yield. Maximum ethanol production was given by immobilized yeast as 7.6% (in 3rd batch, 96 hrs each) a...