Study of Biocatalyst to Produce Ethanol from Starch

Self Cite

This work presents a continuous simultaneous saccharification and fermentation (SSF) process to produce ethanol from starch using glucoamylase and Saccharomyces cerevisiae co-immobilized in pectin gel. The enzyme was immobilized on macroporous silica, after silanization and activation of the support with glutaraldehyde. The silica-enzyme derivative was co-immobilized with yeast in pectin gel. This biocatalyst was used to produce ethanol from liquefied manioc root flour syrup, in three fixed bed reactors. The initial reactor yeast load was 0.05 g wet yeast/ml of reactor (0.1 g wet yeast/g gel), used in all SSF experiments. The enzyme concentration in the reactor was defined by running SSF batch assays, using different amount of silica-enzyme derivative, co-immobilized with yeast in pectin gel. The chosen reactor enzyme concentration, 3.77 U/ml, allowed fermentation to be the rate-limiting step in the batch experiment. In this condition, using initial substrate concentration of 166.0 g/l of total reducing sugars (TRS), 1 ml gel/1 ml of medium, ethanol productivity of 8.3 g/l/h was achieved, for total conversion of starch to ethanol and 91% of the theoretical yield. In the continuous runs, feeding 163.0 g/l of TRS and using the same enzyme and yeast concentrations used in the batch run, ethanol productivity was 5.9 g ethanol/l/h, with 97% of substrate conversion and 81% of the ethanol theoretical yield. Diffusion effects in the extra-biocatalyst film seemed to be reduced when operating at superficial velocities above 3.7 x 10(-4) cm/s.

Section: Trsmentioning

confidence: 99%

“…The presence of calcium in the medium is essential to maintain gel integrity, thus avoiding the leaching of this cation [9].…”

Section: Trsmentioning

confidence: 99%

Section: T (H)mentioning

confidence: 99%

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Continuous Production of Ethanol from Starch Using Glucoamylase and Yeast Co-Immobilized in Pectin Gel

Giordano

Trovati

Schmidell

2007

Self Cite

“…Ethanol production by immobilized yeast cells has been extensively investigated [2][3][4][5][6][7]. For industrial purposes, an important choice criterion is the carrier cost which, combined with the interest in by-products recycling, has been leading to an increasing search for cheap and available potential cell carriers [1].…”

Section: Introductionmentioning

confidence: 99%

Ethanol Production by Fermentation Using Immobilized Cells of Saccharomyces cerevisiae in Cashew Apple Bagasse

Pacheco

Gondim

Gonçalves

2009

In this work, cashew apple bagasse (CAB) was used for Saccharomyces cerevisiae immobilization. The support was prepared through a treatment with a solution of 3% HCl, and delignification with 2% NaOH was also conducted. Optical micrographs showed that high populations of yeast cells adhered to pre-treated CAB surface. Ten consecutive fermentations of cashew apple juice for ethanol production were carried out using immobilized yeasts. High ethanol productivity was observed from the third fermentation assay until the tenth fermentation. Ethanol concentrations (about 19.82-37.83 g L(-1) in average value) and ethanol productivities (about 3.30-6.31 g L(-1) h(-1)) were high and stable, and residual sugar concentrations were low in almost all fermentations (around 3.00 g L(-1)) with conversions ranging from 44.80% to 96.50%, showing efficiency (85.30-98.52%) and operational stability of the biocatalyst for ethanol fermentation. Results showed that cashew apple bagasse is an efficient support for cell immobilization aiming at ethanol production.

“…Immobilization of the enzyme and of the microorganism allows their reutilization, what may turn economically viable the use of high concentrations of biocatalysts in the reactor, reducing reaction times. This technique has been extensively studied in order to reduce process costs [8][9][10][11][12][13].…”

mentioning

confidence: 99%

Improving the Performance of a Continuous Process for the Production of Ethanol from Starch

Trovati

Giordano

2009

Self Cite

In a previous work, a continuous simultaneous saccharification and fermentation process to produce ethanol from cassava starch was studied, using a set of fixed-bed reactors. The biocatalyst consisted of glucoamylase immobilized in silica particles and co-immobilized with S. cerevisiae in pectin gel. Using 3.8 U mL(-1) (reactor) and 0.05 g(wet yeast) mL(-1) (reactor) at start-up, starch hydrolysis was the rate-limiting step. Maximum ethanol productivity was 5.8 g(ethanol) L(-1) h(-1), with 94.0% conversion of total reducing sugars (TRS) and 83.0% of the ethanol theoretical yield. In this work, the molar mass of the substrate and the biocatalyst particle size were reduced in an attempt to improve the bioreactor performance. The diameters of silica and pectin gel particles were reduced from 100 mum and 3-4 mm, respectively, to 60 mum and 1-1.5 mm, and the degree of substrate prehydrolysis by alpha-amylase was increased. The bioreactor performance was assessed for different loads of immobilized glucoamylase (2.1, 2.8, and 3.8 U mL(-1) (reactor)), for the same initial cell concentration (0.05 g(wet yeast.)mL(-1) (reactor)). Feeding with 154.0 g L(-1) of TRS and using 3.8 U mL(-1) (reactor), fermentation became the rate-limiting step. Productivity reached 11.7 g L(-1) h(-1), with 97.0% of TRS conversion and 92.0% of the ethanol theoretical yield. The reactor was operated during 275 h without any indication of destabilization.