ABSTRACT
Organic solvent tolerant microorganism(OSTM) is a novel extremophile and it hasn't been systematically studied until 1980s.Relying on certain mechanisms,the OSTM is able to effectively de-fend and decrease the toxicity from organic solvents,which enable the OSTM to be potentially applied in the industrial fields such as whole-cell catalysis and environmental treatment,etc.The comprehen-sively understanding of the mechanisms involved in organic solvent tolerance of OSTM could be com-bined with genetic engineering in order to modify and optimize the various specifications of OSTM,and further broaden its application in other industrial areas.Latest studies on the tolerant mechanisms of OSTM,in this paper,will be reviewed from four aspects such as vesicle exocytosis and changes of phos-pholipid composition in membrane,etc.Besides,the application of OSTM in whole-cell catalysis and other fields will be introduced.
ABSTRACT
A lipase from Aspergillus niger F044 was purified to homogeneity using ammonium sulfate precipitation, dialysis, DEAE-Sepharose Fast Flow anion exchange chromatography and Sephadex G-75 gel filtration chromatography. This purification protocol resulted in a 73.71-fold purification of lipase with 33.99% final yield, and the relative molecular weight of the enzyme was determined to be approximately 35-40kD using SDS-PAGE. The optimum pH and temperature for lipolytic activity of the lipase was 7.0 and 45 degrees C , respectively. It was extremely stable at 60 degrees C and retained 98.70% of its original activity for 30min. The stability declined rapidly as soon as the temperature rose over 65 degrees C . The lipase was highly stable in the pH range from 2.0 to 9.0 for 4h. Ca2+ and Mg2+ ions stimulated lipolytic activity, whereas Mn2+ , Fe2+ and Zn2+ ions caused inhibition. The values of Km and Vmax calculated from the Lineweaver-Burk plot using pNPP as hydrolysis substrate were 7.37mmol/L and 25.91 micromol/(min x mg), respectively. The N-terminal sequence of the lipase was Ser/Glu/His-Val-Ser-Thr-Ser-Thr-Leu-Asp-Glu-Leu-Gln-Leu-Phe-Ala-Gln, which is highly homogeneity with that of lipase, as reported by Torossian.
Subject(s)
Amino Acid Sequence , Aspergillus niger , Chromatography, Gel , Chromatography, Ion Exchange , Electrophoresis, Polyacrylamide Gel , Enzyme Stability , Fungal Proteins , Chemistry , Metabolism , Hydrogen-Ion Concentration , Lipase , Chemistry , Metabolism , Molecular Sequence Data , Molecular Weight , Sequence Analysis, Protein , TemperatureABSTRACT
Microbial lipases are important industrial biocatalysts with the character of stereoselectivity,site selectivity and high catalytic activity with few side effects.They have been used widely in many industrial and agricultural fields.The technology of protein engineering has been successfully applied to improve the activity and stability of microbial lipases,which will raise the competitive capacity of microbial lipase preparations and enlarge theirs application fields.The strategies,the problems and the prospects of protein engineering technology which have been applied to modify the microbial lipases was surveied.
ABSTRACT
Microbial lipase,one of important industrial biocatalysts,has been used widely in many industrial and agricultural fields.It is always the research focus to screen,mine and develop the microbial lipases with novel catalytic activity and high stability.This paper introduces briefly the pathways and methods to mine novel microbial lipase resources from six aspects,including extremophile,metagenome,genome database,protein engineering,immobilization,chemical modification,etc.
ABSTRACT
A cellulase high-yield strain was identified and named as Trichoderma longibrachiatum SSL by ITS sequence identification. The endoglucanase1 gene (eg1) encoding endo-l,4-?-D-glucanase I was ampli-fied by RT-PCR method, which including 1386 bp and encoding 461 amino acid. Sequence analysis showed that: This gene has a more 90% homology with the T. longibrachiatum eg1 gene. The eg1 gene encoding the mature peptide was inserted into the Pichia pastoris expression vector pPIC9K, which resulted in construc-tion of the recombinant expression plasmid, pPIC9k-eg1. The pPIC9k-eg1 was then introduced into the host Pichia pastoris GS115. After the induction of methanol, extracellular recombinant endoglucanase I from the supernatant of the recombinant Pichia pastoris strain reached 73 U/mL. A clear strengthening of the protein bands, whose molecular weight is about 58 kD, appeared in the SDS-PAGE.
ABSTRACT
Acyl carrier protein is an essential component involved in the biosynthesis of DHA(Docosahexaenoic Acid) via PKS(Polyketide synthase) pathway,which takes the growing acyl chain from one enzyme to another.One cDNA clone,with high homology of ACP,was isolated from Schizochytrium sp.FJU-512 cDNA library.The deduced amino acid sequence contained 142 residues with isoelectric point of 5.04 and had the 4'-phosphopantetheine prosthetic(4'-PP) binding site.The target fragment was digested with BamHⅠ/HindⅢand inserted into the expression vector pET-30a resulting in the plasmid pET-30a/acp.The recombinant vector was transformed into E.coli BL21(DE3) and induced by IPTG.SDS-PAGE analysis demonstrated that ACP was effectively expressed.
ABSTRACT
To improve ethanol production in Saccharomyces cerevisiae,an integration plasmid pUPGKAT with PGK promoter(phosphoglycerate kinase promoter),adh1 gene(the coding sequences of alcohol dehydrogenaseⅠ) and CYC1 terminator(Cytochrome c transcription terminator) was constructed.Firstly,a fusion fragment composed of PGK promoter and adh1 gene was generated by over lap extension PCR and ligated into pUG6 resulting in plasmid pUPGKA.Subsequently,CYC1 termi nator was amplified from pSH65 by PCR and ligated to the SpeⅠand SacⅡrestriction site of pUPGKA.To integrate PGK-adh1-CYC1 into S.cerevisiae genome,pUPGKAT was digested by TthⅢⅠand the lin-earized plasmid was used to transform S.cerevisiae YS2-△adh2(adh2 disrupted strain) by lithium acetate method.The yeast mutant YS2-△adh2-adh1 which had the adh1 gene placed under the PGK promoter and harbored the adh2 deletion was constructed.Anaerobic fermentation showed overexpression of adh1 by PGK promoter resulted in a 8.84% higher ethanol production compared to YS2-△adh2.
ABSTRACT
From the N-terminal amino acid sequence of the Aspergillus niger F044 lipase,a potential homologous gene A84689 to the anl(the gene encoding the Aspergillus niger lipase)was found by means of bioinformatics.Based on the nucleotide sequence of the A84689,primers were designed to amplify anl.Nucleotide sequencing of the genomic anl gene revealed an open reading frame of 1 044 nucleotides,containing three introns(54,45 and 51 nucleotides).The deduced amino acid sequence of the anl gene corresponds to 297 amino acid residues including a signal sequence of 27 amino acid residues.The cloned cDNA coding for mature Anl(the protein of the Aspergillus niger lipase)was overexpressed in Escherichia coli BL21(De3),and the recombinant Anl was purified.The denatured recombinant Anl by 8mol/L urea was refolded in vitro by dilution and DEAE Sepharose Fast Flow chromatography.