Cloning and expression of beta-glucosidase genes in Escherichia coli and Saccharomyces cerevisiae using shuttle vector pYES 2.0.
ABSTRACT Genes for beta-glucosidase (Bgl) isolated from a genomic library of the cellulolytic bacterium, Cellulomonas biazotea, were cloned in pUC18 in its SacI cloning site and transformed to E. coli. Ten putative recombinants showed blackening zones on esculin plates, yellow zones on pNPG plates, in liquid culture and on native polyacrylamide gel electrophoresis activity gels. They fell into three distinct groups. Three representative E. coli clones carried recombinant plasmids designated pRM54, pRM1 and pRM17. The genes were located on 5.6-, 3.7- and 1.84-kb fragments, respectively. Their location was obtained by deletion analysis which revealed that 5.5, 3.2, and 1.8 kb fragments were essential to code for BglA, BglB, and BglC, respectively, and conferred intracellular production of beta-glucosidase on E. coli. Expression of the bgl genes resulted in overproduction of beta-glucosidase in the three clones. Secretion occurred into the periplasmic fractions. Three inserts carrying bgl genes from the representative recombinant E. coli were isolated with SacI, ligated in the shuttle vector pYES 2.0 in its SacI site and transformed to E. coli and S. cerevisiae. The recombinant plasmids were redesignated pRPG1, pRPG2 and pRPG3 coding for BglA1, BglB1 and BglC1. The cloned genes conferred extracellular production of beta-glucosidase on S. cerevisiae and enabled it to grow on cellobiose and salicin. The gall promoter of shuttle vector pYES 2.0 enabled the organisms to produce twice more beta-glucosidase than that supported by the lacZ-promoter of pUC18 plasmid in E. coli. The cloned gene can be used as a selection marker for introducing recombinant plasmids in wild strains of S. cerevisiae. The enzyme produced by bgl+ yeast and E. coli recombinants resembles that of the donor with respect to temperature and pH requirement for maximum activity. Other enzyme properties of the beta-glucosidases from S. cerevisiae were substantially the same as those from C. biazotea.
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ABSTRACT: A 2-deoxyglucose-resistant mutant (M7) of Humicola lanuginosa was obtained by exposing conidia to γ-rays and permitting expression in broth containing 0.6% 2-deoxyglucose (DG) and cellobiose (1%) before plating on DG esculin-ferric ammonium citrate agar medium from which colonies showing faster and bigger blackening zones were selected. Kinetic parameters for enhanced ß-glucosidase (BGL) synthesis by M7 were achieved when corncobs acted as the carbon source. The combination between corncobs and corn steep liquor was the best to support higher values of all product formation kinetic parameters. Effect of temperature on the kinetic and thermodynamic attributes of BGL production equilibrium in the wild organism and M7 was studied using batch process at eight different temperatures in shake-flask studies. The best performance was found at 45°C and 20 g L(-1) corncobs in 64 h. Both growth and product formation (17.93 U mL(-1)) were remarkably high at 45°C and both were coupled under optimum working conditions. Product yield of BGL from the mutant M7 (1556.5 U g(-1) dry corncobs) was significantly higher than the values reported on all fungal and bacterial systems. Mutation had thermo-stabilization influence on the organism and mutant required lower activation energy for growth and lower magnitudes of enthalpy and entropy for product formation than those demanded by the wild organism, other mesophilic and thermo-tolerant organisms. In the inactivation phase, the organisms needed lower values of activation energy, enthalpy and entropy for product formation equilibrium, confirming thermophilic nature of metabolic network possessed by the mutant organism.Brazilian Journal of Microbiology 10/2008; 39(4):724-33. · 0.45 Impact Factor
- Bioscience Biotechnology and Biochemistry 01/2003; 67(1):1-7. · 1.21 Impact Factor
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ABSTRACT: The enzymes used for biomass decomposition comprise a major cost in the production of biofuels from lignocellulosic feedstocks. Engineering of key enzymes de novo in heterologous hosts provides one strategy for the rational improvement of enzyme cocktails. Until recently, Escherichia coli has remained the most commonly used host for recombinant protein expression. Nevertheless, to our knowledge, there are few reports describing the co-expression of biomass degrading enzymes in E. coli. In this study, bicistronic and dual-promoter constructs based on pET30a were built for the co-expression of an endo-β-xylanase gene (xyn) and a β-glucosidase gene (bgl) from Trichoderma reesei QM 9414 in E. coli. The internal ribosome binding site used in the bicistronic constructs was originally found in pET30a. In the dual-promoter constructs described here, a pET30a-derived BioBrick base vector was built for the standard assembly of two targeted genes. Compared with monocistronic constructs, the crude enzyme expressed from a bicistronic construct (xyn located upstream of bgl) and a dual-promoter construct (xyn located upstream of bgl) offered the comparable activity of two recombinant proteins. Our results indicated that the common commercial vectors, such as pET30a, could be modified and optimized for a particular co-expression strategy in E. coli.Biochemical Engineering Journal 10/2012; 68:1–6. · 2.37 Impact Factor