1,721,377 research outputs found
Evaluation of whole Jerusalem artichoke (Helianthus tuberosus L.) for consolidated bioprocessing ethanol production
No full textFor consolidated bioprocessing (CBP), components of Jerusalem artichoke (Helianthus tuberosus L.) tubers and stalks as a potential bioenergy crop were analyzed as carbon and nutrient sources, respectively. The effectiveness of chemical pretreatment with dilute acid or alkali was evaluated to develop a CBP method. Cellulose content, delignification, and enzymatic hydrolysis efficiency of the pretreated stalks were increased more effectively by NaOH treatment than dilute H2SO4 treatment. However, weight loss was greater during alkali pretreatment. Additionally, large volumes of water were required to wash the alkali-treated biomass. Therefore, CBP using the dilute acid-pretreated stalk and the ground tuber of Kluyveromyces marxianus were investigated. Fermentation of both pretreated stalks and tubers by K.marxianus with no nutrient supplementation proceeded acceptably. At 10% (w/v) stalk and 8% (w/v) tuber loading, K.marxianus produced 45.3g/L ethanol after 30h. The ethanol yield was 0.252g ethanol per g dry biomass, or 0.32g ethanol per g fermentable sugars, with a fermentable sugar conversion rate of 60%. These results suggest a cost-effective CBP strategy for bioethanol production from the whole Jerusalem artichoke plant.open
Bioethanol production using the sequential acid/alkali-pretreated empty palm fruit bunch fiber
No full textEmpty palm fruit bunch (EPFB) contains a rigid and ordered fiber structure within a relatively high level of hemicellulose and lignin. To enhance poorly enzymatic digestibility and fermentability, in this a sequential acid/alkali pretreatment strategy was applied to increase the fermentable sugar in EPFB fiber. Cellulose content in the biomass was effectively increased by using dilute sulfuric acid treatment to eliminate hemicellulose followed by highly concentrated sodium hydroxide treatment for delignification. The pretreated biomass consisted of 85.2 ± 1.9% cellulose, 1.8 ± 0.5% hemicellulose, and 9.2 ± 0.3% lignin. Under optimal conditions for enzymatic saccharification, 10% (w/v) of pretreated EPFB fiber was hydrolyzed completely and converted to 70.8 ± 0.8 g/L glucose and 1.8 ± 0.1 g/L xylose with a 83.9% yield efficiency. Simultaneous saccharification and fermentation of the pretreated biomass by Saccharomyces cerevisiae W303-1A produced 37.8 g/L ethanol in 1.5 L fermented medium containing 10% (w/v) pretreated EPFB fiber after 60 h. The ethanol productivity was 0.378 g ethanol/g dry EPFB fiber and 0.45 g ethanol/g glucose after fermentation, with a low concentration of xylose and organic acid metabolites. Also, 88% of fermentable sugar was used by the yeast for ethanol fermentation. These results indicate that sequential acid/alkali pretreatment increased enzymatic digestibility and ethanol productivity.open
Fructose production from Jerusalem artichoke by inulinase immobilized on chitin
No full textInulinase from Aspergillus ficuum was immobilized by cross-linking with glutaraldehyde on chitin. Batch and continuous production of fructose from Jerusalem artichoke tuber was studied using this immobililized inulinase. In a batch reactor, the extent of hydrolysis attained 90% (D-fructose/D-glucose :86/14) in 10h and 77.5g/L of D-fructose was produced from the Jerusalem artichoke tuber juice. In a continuous packed bed column reactor, the maximum volumetric productivity of 61 g/L, h was obtained at residence time of 0.9h and conversion yield of 55%. At a fixed residence time of 2.6 h and 40° C, this could be operated for over two weeks with only a slight loss of activity (4.8%).open
Production of cellulase enzymes during the solid-state fermentation of empty palm fruit bunch fiber
No full textPenicillium verruculosum COKE4E is a fungal strain isolated from bituminous coal. The microorganism cultivated in a minimal medium supplemented with Avicel, carboxymethylcellulose, and oat spelt xylan produced cellulase enzymes as exhibiting carboxymethylcellulase (CMCase), Avicelase, xylanase, and cellobiosidase activities. In this study, the productivity of the extracellular enzymes in the strain was evaluated by using empty palm fruit bunch fiber (EPFBF), a lignocellulosic biomass, as a substrate for solid-state bioconversion. The highest cellulase activities were observed after 6 days of fermentation at pH 6.0 and 30 °C. The enzymes were secreted as cellulosomes for the degradation of EPFBF as a sole carbon source. Focused ion beam analysis showed that P. verruculosum COKE4E produced cellulolytic enzymes that were able to effectively biodegrade EPFBF during solid-state fermentation. In this process, 6.5 U of CMCase, 6.8 U of Avicelase, and 8.8 U of xylanase per gram of dry solid EPFBF were produced. These results demonstrate that EPFBF may be a potential raw material in solid-state fermentation for the production of cellulase enzymes to be used for biofuel production.open
Enzymatic conversion of ethanol into acetaldehyde in a gas-solid bioreactor
No full textThe enzymatic conversion of ethanol into acetaldehyde using dried
whole cells of Hansenuta polymorpha was tried in a gas-solid bioreactor. The
bioreactor could be mainlined stably over one month at 35~ with complete conversion
in the water content under 8% without any serious problems.open
Ethanol production from Jerusalem artichoke by inulinase and Zymomonas mobilis
No full textEthanol production from Jerusalem artichoke was studied using inulinase and Z.mobilis by simultaneous saccharification and fermentation (SSF) process. The SSF process showed higher ethanol yield and productivity than the acid or enzymatic prehydrolyzed two-step process. The optimum temperature and inulinase concentration for SSF were 35°C and 0.25% (v/w, 4.4 units/g of sugar), respectively. In order to operate the SSF process in a continuous mode, inulinase and Z.mobilis cells were coimmobilized in alginate beads, using chitin as a matrix for enzyme immobilization. The maximum ethanol productivity of the continuous SSF process was 55.1 g/L/h, with 55% conversion yield. At the conversion yield of 90%, the productivity was 32.7 g/L/h. The continuous SSF system could be operated stably over 2 wk with an ethanol concentration of 48.6 g/L (95% of theoretical yield).open
Process development for simultaneous starch saccharification and ethanol fermentation by Zymomonas mobilis
No full textVarious simultaneous starch saccharification and ethanol fermentation (SSSF) processes were developed and evaluated on batch, semibatch and continuous modes of fermentation in laboratory and pilot scale fermentors using Zymomonas mobilis. Compared with a two-step process involving separate saccharification and fermentation stages, the SSSF reduced the total process time by half. In order to produce ethanol from sago starch economically, the immobilization of amyloglucosidase and Z. mobilis cells was studied. Among the various immobilization methods tested, a co-immobilized system using chitin and sodium alginate appeared most promising with respect to ethanol productivity and operational stability. In order to scale-up the SSSF process, large scale SSSF processes were studied in batch and semibatch fermentation modes. In pilot scale SSSFs, the kinetic results were found to be similar to those from laboratory scale fermentation. Finally, a mathematical model was described for the SSSF process. Simulations of glucose concentration and other fermentation parameters agreed closely with experimental results.open
Statistical optimization of medium for the production of recombinant hirudin from Saccharomyces cerevisiae using response surface methodology
No full textAn efficient fermentation medium producing a colourless product with high yields has been developed for the production of recombinant hirudin from Saccharomyces cerevisiae. Response surface methodology was applied to optimize the medium constituents. A 25-1 fractional factorial central composite design has been chosen to explain the combined effect of the six medium constituents, viz. yeast extract, peptone, casamino acids, ammonium sulphate, potassium phosphate and galactose, and to design a minimum number of experiments. The optimized medium produced 65.3 mg/l of r-hirudin in shake flask culture, which is 35% higher than the unoptimized medium. The colour of the purified product was influenced by the colour intensity of culture supernatant, which in turn depended upon the concentration of complex substrates used in the medium. The concentration of yeast extract has been reduced to 16 g/l in the optimized medium than other reported media containing 40 g/l yeast extract. The colour intensity of culture supernatant obtained by the optimized medium was reduced by 60% from the reported media containing 40 g/l yeast extract.open
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