Ethanol is the main byproduct of anaerobic H2-producing fermentation in Klebsiella oxytoca HP1. Two moles of NAD(P)H are consumed to yield one mole of ethanol that may decrease bacterial hydrogen production. In this a...Ethanol is the main byproduct of anaerobic H2-producing fermentation in Klebsiella oxytoca HP1. Two moles of NAD(P)H are consumed to yield one mole of ethanol that may decrease bacterial hydrogen production. In this article the adhE gene that codes for acetaldehyde dehydrogenase was disrupted for the first time. A homologous recombination vector pTA-Str was constructed in which the adhE gene was disrupted by inserting an aminoglycoside-3'-adenyltransferase (aadA) gene. As expected, the vector includes the insertion 5′-adhE-aadA-adhE-3′. The amplified DNA fragment 5′-adhE-aadA-adhE-3′ from pTA-Str was transformed into K. oxytoca HP1 and one recombinant was obtained. PCR analysis of the resulting genomic DNA indicated the appropriate deletion and insertion. Compared with the H2-production of wild type K. oxytoca HP1, the hydrogen yield of the mutant increased by 16.07% and ethanol concentration decreased by 77.47%, suggesting that inactivation of the adhE gene in K. oxy- toca HP1 is a potential method for enhancing bacterial H2-production.展开更多
Cellulose is a kind of renewable resource that is abundant in nature.It can be degraded by microorganisms such as mildew.A mildew strain with high cellulase activity was isolated from mildewy maize cob and classified ...Cellulose is a kind of renewable resource that is abundant in nature.It can be degraded by microorganisms such as mildew.A mildew strain with high cellulase activity was isolated from mildewy maize cob and classified as Aspergillus glaucus XC9 by morphological and 18S rRNA gene sequence analyses.We studied the effects of nitrogen source,initial pH,temperature,incubation time,medium composition,and surfactants on cellulase production.Maximal activities of carboxymethylcellulase(6,812 U/g dry koji)and filter paperase(172 U/g dry koji)were obtained in conditions as follows:initial pH,5.5–6.0;temperature,30℃;cultivation period,3–4 days;inoculum ratio,6%(vol/vol);sugarcane bagasse/wheat bran ratio,4:6.When bagasse was used as substrate and mixed with wet koji at a 1:1(wt/wt)ratio,the yield of reducing sugars was 36.4%.The corresponding conversion rate of cellulose to reducing sugars went as high as 81.9%.The results suggest that A.glaucus XC9 is a preferred candidate for cellulase production.展开更多
It is of great significance to reveal a key agent to improve the efficiency of conversion of lignocellulosic biomass to fermentable sugars for the production of bioethanol.This study investigated a two-stage pretreatm...It is of great significance to reveal a key agent to improve the efficiency of conversion of lignocellulosic biomass to fermentable sugars for the production of bioethanol.This study investigated a two-stage pretreatment of bamboo comprising a microbial treatment using Ceriporiopsis sp.followed by a hydrothermal treatment to facilitate the process with Mn^(2+)as an accelerator.The effects of Mn^(2+)nutritional addition on ligninolytic activity,lignin degradation,total weight loss,pulp yield,sugar yield and sugars in the soluble fraction were examined.The results showed that the time required for the incubations supplemented with Mn^(2+)to achieve sufficient lignin degradation and sugar yield from both the pulp and soluble fractions was significantly shortened,whereas all three ligninolytic activities were significantly decreased.The enzyme activity varied according to the presence of Mn^(2+),although the amount and species of the expressed protein are similar.Considering the cost,microbial treatment with a one-time fed-batch supply of metal nutrition(MnSO4)was the most preferable contribution to hydrothermal pretreatment,resulting in 19.7%lignin degradation,66.7%pulp yield and 26.1%sugar yield over a period of 21 d.It was proven that microbial treatment by solid state incubation with Mn^(2+)nutrition has the potential to be a low-cost,environmentally friendly alternative to chemical approaches.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 30470395)the Key Science and Technology Project of Fujian (Grant No. 2005I106)
文摘Ethanol is the main byproduct of anaerobic H2-producing fermentation in Klebsiella oxytoca HP1. Two moles of NAD(P)H are consumed to yield one mole of ethanol that may decrease bacterial hydrogen production. In this article the adhE gene that codes for acetaldehyde dehydrogenase was disrupted for the first time. A homologous recombination vector pTA-Str was constructed in which the adhE gene was disrupted by inserting an aminoglycoside-3'-adenyltransferase (aadA) gene. As expected, the vector includes the insertion 5′-adhE-aadA-adhE-3′. The amplified DNA fragment 5′-adhE-aadA-adhE-3′ from pTA-Str was transformed into K. oxytoca HP1 and one recombinant was obtained. PCR analysis of the resulting genomic DNA indicated the appropriate deletion and insertion. Compared with the H2-production of wild type K. oxytoca HP1, the hydrogen yield of the mutant increased by 16.07% and ethanol concentration decreased by 77.47%, suggesting that inactivation of the adhE gene in K. oxy- toca HP1 is a potential method for enhancing bacterial H2-production.
基金supported by grants from the National High Technology Research and Development Program of China (863 Program,No.2001AA515040)the Science and Technology Cooperation Project between the Chinese and Hungarian Governments (3502Z20031108)the Science and Technology Project of Xiamen (3502Z20041070).
文摘Cellulose is a kind of renewable resource that is abundant in nature.It can be degraded by microorganisms such as mildew.A mildew strain with high cellulase activity was isolated from mildewy maize cob and classified as Aspergillus glaucus XC9 by morphological and 18S rRNA gene sequence analyses.We studied the effects of nitrogen source,initial pH,temperature,incubation time,medium composition,and surfactants on cellulase production.Maximal activities of carboxymethylcellulase(6,812 U/g dry koji)and filter paperase(172 U/g dry koji)were obtained in conditions as follows:initial pH,5.5–6.0;temperature,30℃;cultivation period,3–4 days;inoculum ratio,6%(vol/vol);sugarcane bagasse/wheat bran ratio,4:6.When bagasse was used as substrate and mixed with wet koji at a 1:1(wt/wt)ratio,the yield of reducing sugars was 36.4%.The corresponding conversion rate of cellulose to reducing sugars went as high as 81.9%.The results suggest that A.glaucus XC9 is a preferred candidate for cellulase production.
基金the research fund from the Xiamen Southern Oceanographic Center(No.14GZP59HJ29)Fujian Provincial Department of Ocean and Fisheries(No.2015-27)President Fund of Xiamen University(20720150090).
文摘It is of great significance to reveal a key agent to improve the efficiency of conversion of lignocellulosic biomass to fermentable sugars for the production of bioethanol.This study investigated a two-stage pretreatment of bamboo comprising a microbial treatment using Ceriporiopsis sp.followed by a hydrothermal treatment to facilitate the process with Mn^(2+)as an accelerator.The effects of Mn^(2+)nutritional addition on ligninolytic activity,lignin degradation,total weight loss,pulp yield,sugar yield and sugars in the soluble fraction were examined.The results showed that the time required for the incubations supplemented with Mn^(2+)to achieve sufficient lignin degradation and sugar yield from both the pulp and soluble fractions was significantly shortened,whereas all three ligninolytic activities were significantly decreased.The enzyme activity varied according to the presence of Mn^(2+),although the amount and species of the expressed protein are similar.Considering the cost,microbial treatment with a one-time fed-batch supply of metal nutrition(MnSO4)was the most preferable contribution to hydrothermal pretreatment,resulting in 19.7%lignin degradation,66.7%pulp yield and 26.1%sugar yield over a period of 21 d.It was proven that microbial treatment by solid state incubation with Mn^(2+)nutrition has the potential to be a low-cost,environmentally friendly alternative to chemical approaches.
