PRODUCTION OF ETHANOL BY FED-BATCH FERMENTATION

The production of ethanol, from glucose in batch and fed batch culture, was investigated. In the fed batch culture, the glucose feeding was added into the culture at 16th hour of fermentation. The effects of different glucose concentration feeding rates on ethanol fermentation were investigated for fed batch culture. The 2gL-1hr-1 glucose concentration feeding rate was found to give higher ethanol yield (2.47 g ethanol g glucose-1), with respect to substrate consumed as compared to 8 gL-1hr-1 (0.23 g ethanol g glucose-1) and 4 gL-1hr-1 (0.20 g ethanol g glucose-1). The ethanol yield with respect to substrate consumed obtained in batch culture was 0.81 g ethanol g glucose-1. The fed batch culture at 2 gL-1hr-1 glucose concentration feeding rate was proven to be a better fermentation system than the batch culture. The specific growth rate, specific glucose consumption rate and specific ethanol production rate for the fed batch fermentation, at 2 gL-1hr-1 glucose concentration feeding rate, were 0.065 hr-1, 1.20 hr-1 and 0.0009 hr-1, respectively

The evaluation of various kinetic models for base-catalyzed ethanolysis of palm oil

In this paper, the kinetics of palm oil ethanolysis with various models have been investigated in a temperature range of 25-55 degrees C. The highest yield was achieved when the conversion to ethyl ester was 97.5+/-0.5 in the stated temperature range, using ethanol:oil molar ratio of 12:1, and 1.0 wt. sodium ethoxide. The level of conformity of the reaction with reversible second order, irreversible second order and first order kinetic models were evaluated by means of the R-2 values of the linear curves. The ethanolysis showed the best conformity with irreversible second order kinetic model with 92-98 level of confidence. The reaction rate constants were within 0.018-0.088 dm(3)/mol min and the activation energy of the reaction was 42.36 kJ/mol

Ionic liquid-mediated solid acid saccharification of sago waste: Kinetic, ionic liquid recovery and solid acid catalyst reusability study

Dissolved carbohydrate obtained from 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) pretreated sago waste was saccharified by Amberlyst 15 (A15) to study the kinetics of the ionic liquid-mediated solid acid saccharification of the lignocellulosic biomass. Besides the kinetics of both reducing sugars production and reducing sugars degradation reactions, emphasis was given to the recovery and reusability of the ionic liquid and solid acid catalyst. The hydrolysis reaction follows a first order sugars production-first order sugars degradation reaction that agreed well with the generalized Saeman kinetic model. Both the rates of reducing sugars production and degradation varied with temperature and catalyst loading. Higher temperature and catalyst loading promoted the rates of sugars production reaction more than the rate of degradation reaction. This is evident from the relatively larger rate constant of sugars production (k(1)) than the rate constant of degradation (k(2)). The activation energy for sugars production and degradation was 125.1 kJ mol(-1) and 60.8 kJ mol(-1) respectively. These values are lower than the literature reported values for sulfuric acid-catalyzed saccharification confirming its employment suitability for reducing sugars production. The good recovery of [BMIM]Cl and good reusability of A15 further substantiated the feasibility of the process. The recovery of ionic liquid was improved by employing a multiple step aqueous biphasic system in this study. Approximately 60% of the ionic liquid was recovered by 3-step aqueous biphasic system. This finding is on par with the reported literatures using aqueous biphasic system to recover ionic liquid. Equally robust, the solid acid catalyst regained its saccharification performance after regeneration for a total of three cycles. (C) 2015 Elsevier B.V. All rights reserved

Process optimization and kinetics of microwave assisted transesterification of crude glycerol for the production of glycerol carbonate

The production of glycerol carbonate (GC) from industrial grade crude glycerol was catalyzed by calcium oxide (CaO) via microwave assisted transesterification (MAT). Influencing process parameters including reaction temperature, time and molar ratio of dimethyl carbonate/glycerol (DMC/Gly) were examined and optimized by applying Box Behnken Design (BBD). The reaction was modelled into a reduced cubic model with good predictive accuracy. A high GC yield of 99.5% was achieved with 1 wt% CaO at optimized conditions such as reaction temperature of 65 °C, reaction time of 3 min and DMC/Gly molar ratio of 2.5. The study performed on the reaction kinetics suggests that the reaction follows an irreversible second order rate equation. A relatively low activation energy of 4.53 kJ mol-1 was determined for the microwave assisted transesterification of crude glycerol for the production of GC. The values of rate constants between 45 °C to 65 °C were in the range of 0.023-0.026 L mol-1 min-1, which are of one magnitude order higher than that of the conventional heating

Ragi tapai and Saccharomyces cerevisiae as potential coculture in viscous fermentation medium for ethanol production

A comparison study on the ethanol production from 20% (w/v) of unhydrolyzed raw cassava starch using Saccharomyces cerevisiae and Candida tropicalis was performed and compared with the commercialized ragi tapai. The findings showed that S. cerevisiae, C. tropicalis and ragi tapai produced 23, 20 mg/l and 26 g/l of ethanol in 72 h, respectively. Subsequent coculturing of the two best performing strains namely ragi tapai and S. cerevisiae were performed to improve ethanol production and to reduce the accumulation of inhibitory concentration of reducing sugar with 10% (w/v) unhydrolyzed raw cassava starch. The coculture of ragi tapai with S. cerevisiae using the unhydrolyzed raw starch in a single step-fermentation produced an ethanol concentration of 35 g/l when the starch was inoculated with ragi tapai and cocultured with S. cerevisiae. The yield was 46% higher than the one inoculated with ragi tapai only (24 g/l). The glucose concentration was maintained at a low concentration in the coculture medium as compared to the medium with pure ragi tapai. The findings suggested that coculture of ragi tapai with S. cerevisiae is capable of enhancing the ethanol production and prevention of the inhibitory effect of reducing sugars on amylolytic activity

Conversion of Fibrous Sago (Metroxylon sagu) Waste into Fermentable Sugar via Acid and Enzymatic Hydrolysis

The hydrolysis of dried-powdered fibrous sago waste by sulphuric acid and glucoamylase was studied. Both studies were carried out in an Erlenmeyer flask placed in a controlled temperature water bath. Samples were taken from the reaction flask at every 30 min interval for reducing sugar determination. The optimum condition for acid hydrolysis was found to be at 90°C, using 1.5 M acid concentration and reaction time of 120 min yielding 0.6234 g glucose g-1 waste. The kinetic parameters of acid hydrolysis in the Saeman`s model, were the rate constant (k1 = 0.01405 (1/min)), activation energy (Ea =120.40 (kJ mol-1)) and pre-exponential factor (A = 9.52x1016 (1/min)). The optimum condition for enzymatic hydrolysis using glucoamylase was found to be at enzyme concentration of 6 AGU mL-1 and reaction time of 30 min, yielding 0.5646 g glucose g-1 waste. The kinetic parameters in the competitive inhibition model corresponding to the optimum condition, namely the equilibrium constant for enzyme-inhibitor complex, Michaelis-Menten constant and maximum velocity, are 1.4727, 0.24175 and 1.35460 g L-1.min, respectively

An observation on sludge granulation in an enhanced biological phosphorus removal process

A sequencing batch reactor (SBR) seeded with flocculated sludge and fed with synthetic wastewater was operated for an enhanced biological phosphorus removal (EBPR) process. Eight weeks after reactor startup, sludge granules were observed. The granules had a diameter of 0.5 to 3.0 mm and were brownish in color and spherical or ellipsoidal in shape. No significant change was observed in sludge granule size when operational pH was changed from 7 to 8. The 208-day continuous operation of the SBR showed that sludge granules were stably maintained with a sludge volume index (SVI) between 30 to 55 mL/g while securing a removal efficiency of 83% for carbon and 97% for phosphorus. Fluorescent in situ hybridization (FISH) confirmed the enrichment of polyphosphate accumulating organisms (PAOs) in the SBR. The observations of sludge granulation in this study encourage further studies in the development of granules-based EBPR process

Publisher Correction: Whole-genome sequencing of a sporadic primary immunodeficiency cohort (Nature, (2020), 583, 7814, (90-95), 10.1038/s41586-020-2265-1)

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