A self-made lipase preparation from Candida sp. 99-125 was used for the production of biodiesel through enzymatic esterification of fatty acids. The crude lipase powder and fermentation broth were immobilized on a che...A self-made lipase preparation from Candida sp. 99-125 was used for the production of biodiesel through enzymatic esterification of fatty acids. The crude lipase powder and fermentation broth were immobilized on a cheap fiber cloth carrier. The conditions of lipase-catalyzed esterification between long-chain fatty acids and methanol in a solvent system were investigated in detail, including the temperature, pH value, substrate concentration, solvent, absorbent agent, enzyme dosage and purity, immobilization method, the mode of addition of substrate. The results show that reaction temperature, pH of lipase micro-environment, substrate concentration, enzyme dosage and purity affect the esterification strongly. Several new methods and enzymatic procedures for improving the enzymatic reaction involving the process cost are also discussed, such as fossil diesel fuel as reaction solvent, immobilization method, multi-step gradient addition of methanol. The esterification degree of 92.8% was obtained with oleic acid and methanol under the optimal reaction condition after 12.5 h reaction time. The half-life of the immobilized lipase preparation from crude free lipase powder for esterification was 15 days.展开更多
In ethanol fermentation of Saccharomyces cerevisiae (S. cerevisiae), glycerol is one of the main by-products. The purpose of this investigation was to increase ethanol yield through minimizing glycerol yield by usin...In ethanol fermentation of Saccharomyces cerevisiae (S. cerevisiae), glycerol is one of the main by-products. The purpose of this investigation was to increase ethanol yield through minimizing glycerol yield by using mutants in which FPS1 encoding a channel protein that mediates glycerol export and GPD2 encoding one of glycerol-3-phosphate dehydrogenase were knocked-out using one-step gene replacement. GLT1 and GLN1 that encode glutamate synthase and glutamine synth.etase, respectively,were overexpressed using two-step gene replacment in fpsl△gpd2△ mutant.The fermentation properties of ZAL69(fpsl△::LEU2 gpd2△::URA3) and ZAL808 (fps1△::LEU2 gpd2△::URA3 PPGK1-GLT1 PPGK1-GLN1) under microaerobic conditions were investigated and compared with those of wild type(DC124). Consumption of glucose, yield of ethanol, yield of glycerol, acetic acid, and pyruvic acid were monitored. Compared with wild type, the ethanol yield of ZAL69 and ZAL808 were improved by. 13.17% and 6.66 %, respectively, whereas glycerol yield decreased by 37.4 % and 41.7 %. Meanwhile, acetic acia yield and pyruvic acid yield aecreasea aramatlcally comparea to wild type. Our results indicate that FPS1 and GPD2 deletion of S. cerevisiae resulted in reduced glycerol yield and increased ethanol yield, but simultaneous overexpression of GLT1 and GLN1 infps1△gpd2△ mutant did not have a higher ethanol yield thanfps1△gpd2△ mutant.展开更多
Serratia marcescens ECUI010, as an extracellular lipase and a significant catalyst, which had been widely employed to catalyze various chemical reactions such as non-specific, stereo-specific hydrolysis and esterifica...Serratia marcescens ECUI010, as an extracellular lipase and a significant catalyst, which had been widely employed to catalyze various chemical reactions such as non-specific, stereo-specific hydrolysis and esterification for industrial biocatalytic applications, was previously mostly expressed intracellularly as inclusion bodies in Escherichia coli. Denaturation and renaturation of inclusion bodies had a significant influence on the lipase activity. Thereupon, our present work described the secretion expression of gene encoding of this lipase in Pichia pastoris GS 115 and characterization of the recombinant enzyme. Firstly, the obtained lipA gene fragment was introduced into P. pastoris expression vector pPIC9K, the lipA gene without its signal sequence were cloned downstream to the alpha-mating factor signal and expressed in P. pastoris GS115 under the control of AOXI promoter, and the recombinant plasmid pPIC9K-lipA was transformed into P. pastoris strain GS115 by electroporation, and this recombinant P. pastoris were identified by PCR. Then lipase activity was detected on BMMY-tributyrin and olive oil agar plates containing Rhodamine B. Transformants with lipase activity by screening were induced 6 days by methanol, one band of 77 kDa protein could be observed by 10% SDS-PAGE. p-nitrophenyl esters of fatty acids were used as the substrates in an automated activity assay of liquid culture media. The pH and temperature optimum of lipase were pH 8.5 and 40℃ respectively. The stability and effects of metal ions and other reagents were also determined. However, the recombinant fusion intended for secretion was efficiently secreted in a percentage of close to 90% and remained stable even in rich medium at high cell density cultures, yielding values of over 4 U of lipase activity per milliliter of culture media supernatant.展开更多
The heat exchanger network(HEN) synthesis problem based on entransy theory is analyzed. According to the characteristics of entransy representation of thermal potential energy, the entransy dissipation represents the ...The heat exchanger network(HEN) synthesis problem based on entransy theory is analyzed. According to the characteristics of entransy representation of thermal potential energy, the entransy dissipation represents the irreversibility of the heat transfer process, the temperature difference determines the entransy dissipation, and four HEN design steps based on entransy theory are put forward. The present study shows how it is possible to set energy targets based on entransy and achieve them with a network of heat exchangers by an example of heat exchanger network design for four streams. In order to verify the correctness of the heat exchanger networks design method based on entransy theory, the synthesis of the HEN for the diesel hydrogenation unit is studied. Using the heat exchange networks design method based on entransy theory, the HEN obtained is consistent with energy targets. The entransy transfer efficiency of HEN based on entransy theory is 92.29%, higher than the entransy transfer efficiency of the maximum heat recovery network based on pinch technology.展开更多
The study was aimed to evaluate the effect of replacement time and rate of soybean oil by flax oil (FO) on polyunsaturated fatty acid (PUFA) profile in egg of laying hens. Two hundred White Leghorn hens with 30 we...The study was aimed to evaluate the effect of replacement time and rate of soybean oil by flax oil (FO) on polyunsaturated fatty acid (PUFA) profile in egg of laying hens. Two hundred White Leghorn hens with 30 weeks of age were divided into five treatments with four replicates of l 0 birds each. Treatments were assigned randomly and consisted of 0.00%, 0.75%, 1.50%, 2.25% and 3.00% FO in commercial corn-soybean meal diets, in which the soybean oil was partially replaced. The experiment was conducted for 90 d. The main research findings were that feed intake, egg production rate, egg weight and feed conversion were not influenced by time and dietary treatment. Fatty acid content was significantly altered (P 〈 0.05) by FO, showing a progressive increase in egg n-3 fatty acid (especially docosahexaenoic acids (DHA) and eicosapentaenoic acids (EPA)) when FO was added. Levels of EPA and DHA were higher (P 〈 0.05) in the egg lipids of FO fed hens than those in the control group. However, no significant differences were observed either in egg weight or egg production among groups. The highest incorporation (P 〈 0.05) of total n-3 fatty acid content in eggs was obtained with 3% FO/kg. This increase was proportional to FO inclusion levels in the diets.展开更多
The non-edible crude rice bran oil was extracted from white rice bran, and then was catalyzed by immobilized lipase for biodiesel production in this study. The effects of water content, oil/methanol molar ratio, tempe...The non-edible crude rice bran oil was extracted from white rice bran, and then was catalyzed by immobilized lipase for biodiesel production in this study. The effects of water content, oil/methanol molar ratio, temperature, enzyme amount, solvent,number of methanol added times and two-step methanolysis by using Candida sp. 99-125 as catalyst were investigated. The optimal conditions for processing 1 g rice bran oil were: 0.2 g immobilized lipase, 2 ml n-hexane as solvent, 20% water based on the rice bran oil mass, temperature of 40 °C and two-step addition of methanol. As a result, the fatty acid methyl esters yield was 87.4%. The immobilized lipase was proved to be stable when it was used repeatedly for 7 cycles.展开更多
基金Supported by the National Natural Science Foundation of China (No. 20176020) and 863 Hi-Technology Research and Deve-lopment Program of China (No. 2002AA514030)
文摘A self-made lipase preparation from Candida sp. 99-125 was used for the production of biodiesel through enzymatic esterification of fatty acids. The crude lipase powder and fermentation broth were immobilized on a cheap fiber cloth carrier. The conditions of lipase-catalyzed esterification between long-chain fatty acids and methanol in a solvent system were investigated in detail, including the temperature, pH value, substrate concentration, solvent, absorbent agent, enzyme dosage and purity, immobilization method, the mode of addition of substrate. The results show that reaction temperature, pH of lipase micro-environment, substrate concentration, enzyme dosage and purity affect the esterification strongly. Several new methods and enzymatic procedures for improving the enzymatic reaction involving the process cost are also discussed, such as fossil diesel fuel as reaction solvent, immobilization method, multi-step gradient addition of methanol. The esterification degree of 92.8% was obtained with oleic acid and methanol under the optimal reaction condition after 12.5 h reaction time. The half-life of the immobilized lipase preparation from crude free lipase powder for esterification was 15 days.
基金the National High Technology Research and Development Program of China(2002AA647040)
文摘In ethanol fermentation of Saccharomyces cerevisiae (S. cerevisiae), glycerol is one of the main by-products. The purpose of this investigation was to increase ethanol yield through minimizing glycerol yield by using mutants in which FPS1 encoding a channel protein that mediates glycerol export and GPD2 encoding one of glycerol-3-phosphate dehydrogenase were knocked-out using one-step gene replacement. GLT1 and GLN1 that encode glutamate synthase and glutamine synth.etase, respectively,were overexpressed using two-step gene replacment in fpsl△gpd2△ mutant.The fermentation properties of ZAL69(fpsl△::LEU2 gpd2△::URA3) and ZAL808 (fps1△::LEU2 gpd2△::URA3 PPGK1-GLT1 PPGK1-GLN1) under microaerobic conditions were investigated and compared with those of wild type(DC124). Consumption of glucose, yield of ethanol, yield of glycerol, acetic acid, and pyruvic acid were monitored. Compared with wild type, the ethanol yield of ZAL69 and ZAL808 were improved by. 13.17% and 6.66 %, respectively, whereas glycerol yield decreased by 37.4 % and 41.7 %. Meanwhile, acetic acia yield and pyruvic acid yield aecreasea aramatlcally comparea to wild type. Our results indicate that FPS1 and GPD2 deletion of S. cerevisiae resulted in reduced glycerol yield and increased ethanol yield, but simultaneous overexpression of GLT1 and GLN1 infps1△gpd2△ mutant did not have a higher ethanol yield thanfps1△gpd2△ mutant.
文摘Serratia marcescens ECUI010, as an extracellular lipase and a significant catalyst, which had been widely employed to catalyze various chemical reactions such as non-specific, stereo-specific hydrolysis and esterification for industrial biocatalytic applications, was previously mostly expressed intracellularly as inclusion bodies in Escherichia coli. Denaturation and renaturation of inclusion bodies had a significant influence on the lipase activity. Thereupon, our present work described the secretion expression of gene encoding of this lipase in Pichia pastoris GS 115 and characterization of the recombinant enzyme. Firstly, the obtained lipA gene fragment was introduced into P. pastoris expression vector pPIC9K, the lipA gene without its signal sequence were cloned downstream to the alpha-mating factor signal and expressed in P. pastoris GS115 under the control of AOXI promoter, and the recombinant plasmid pPIC9K-lipA was transformed into P. pastoris strain GS115 by electroporation, and this recombinant P. pastoris were identified by PCR. Then lipase activity was detected on BMMY-tributyrin and olive oil agar plates containing Rhodamine B. Transformants with lipase activity by screening were induced 6 days by methanol, one band of 77 kDa protein could be observed by 10% SDS-PAGE. p-nitrophenyl esters of fatty acids were used as the substrates in an automated activity assay of liquid culture media. The pH and temperature optimum of lipase were pH 8.5 and 40℃ respectively. The stability and effects of metal ions and other reagents were also determined. However, the recombinant fusion intended for secretion was efficiently secreted in a percentage of close to 90% and remained stable even in rich medium at high cell density cultures, yielding values of over 4 U of lipase activity per milliliter of culture media supernatant.
基金Supported the National Natural Science Foundation of China(21406124)
文摘The heat exchanger network(HEN) synthesis problem based on entransy theory is analyzed. According to the characteristics of entransy representation of thermal potential energy, the entransy dissipation represents the irreversibility of the heat transfer process, the temperature difference determines the entransy dissipation, and four HEN design steps based on entransy theory are put forward. The present study shows how it is possible to set energy targets based on entransy and achieve them with a network of heat exchangers by an example of heat exchanger network design for four streams. In order to verify the correctness of the heat exchanger networks design method based on entransy theory, the synthesis of the HEN for the diesel hydrogenation unit is studied. Using the heat exchange networks design method based on entransy theory, the HEN obtained is consistent with energy targets. The entransy transfer efficiency of HEN based on entransy theory is 92.29%, higher than the entransy transfer efficiency of the maximum heat recovery network based on pinch technology.
文摘The study was aimed to evaluate the effect of replacement time and rate of soybean oil by flax oil (FO) on polyunsaturated fatty acid (PUFA) profile in egg of laying hens. Two hundred White Leghorn hens with 30 weeks of age were divided into five treatments with four replicates of l 0 birds each. Treatments were assigned randomly and consisted of 0.00%, 0.75%, 1.50%, 2.25% and 3.00% FO in commercial corn-soybean meal diets, in which the soybean oil was partially replaced. The experiment was conducted for 90 d. The main research findings were that feed intake, egg production rate, egg weight and feed conversion were not influenced by time and dietary treatment. Fatty acid content was significantly altered (P 〈 0.05) by FO, showing a progressive increase in egg n-3 fatty acid (especially docosahexaenoic acids (DHA) and eicosapentaenoic acids (EPA)) when FO was added. Levels of EPA and DHA were higher (P 〈 0.05) in the egg lipids of FO fed hens than those in the control group. However, no significant differences were observed either in egg weight or egg production among groups. The highest incorporation (P 〈 0.05) of total n-3 fatty acid content in eggs was obtained with 3% FO/kg. This increase was proportional to FO inclusion levels in the diets.
基金Supported by the National High Technology Research and Development Program of China (2006AA020101, 2007AA10Z360,2009AA03Z232)Key Projects in the National Science & Technology Pillar Program during the Eleventh Five-Year Plan Period (2008BA163B07)
文摘The non-edible crude rice bran oil was extracted from white rice bran, and then was catalyzed by immobilized lipase for biodiesel production in this study. The effects of water content, oil/methanol molar ratio, temperature, enzyme amount, solvent,number of methanol added times and two-step methanolysis by using Candida sp. 99-125 as catalyst were investigated. The optimal conditions for processing 1 g rice bran oil were: 0.2 g immobilized lipase, 2 ml n-hexane as solvent, 20% water based on the rice bran oil mass, temperature of 40 °C and two-step addition of methanol. As a result, the fatty acid methyl esters yield was 87.4%. The immobilized lipase was proved to be stable when it was used repeatedly for 7 cycles.