Characterization of endo-β-1,4-glucanase from a novel strain of Penicillium pinophilum KMJ601

Biochemical Characterization of Novel GH6 Endoglucanase from Myxococcus sp. B6-1 and Its Effects on Agricultural Straws Saccharification

Cellulase has been widely used in many industrial fields, such as feed and food industry, because it can hydrolyze cellulose to oligosaccharides with a lower degree of polymerization. Endo-β-1,4-glucanase is a critical speed-limiting cellulase in the saccharification process. In this study, endo-β-1,4-glucanase gene (CelA257) from Myxococcus sp. B6-1 was cloned and expressed in Escherichia coli. CelA257 contained carbohydrate-binding module (CBM) 4-9 and glycosyl hydrolase (GH) family 6 domain that shares 54.7% identity with endoglucanase from Streptomyces halstedii. The recombinant enzyme exhibited optimal activity at pH 6.5 and 50 °C and was stable over a broad pH (6-9.5) range and temperature < 50 °C. CelA257 exhibited broad substrate specificity to barley β-glucan, lichenin, CMC, chitosan, laminarin, avicel, and phosphoric acid swollen cellulose (PASC). CelA257 degraded both cellotetrose (G₄) and cellppentaose (G₅) to cellobiose (G₂) and cellotriose (G₃). Adding CelA257 increased the release of reducing sugars in crop straw powers, including wheat straw (0.18 mg/mL), rape straw (0.42 mg/mL), rice straw (0.16 mg/mL), peanut straw (0.16 mg/mL), and corn straw (0.61 mg/mL). This study provides a potential additive in biomass saccharification applications.

A Novel Cellobiohydrolase I (CBHI) from Penicillium digitatum: Production, Purification, and Characterization

A new cellulase producer strain of Penicillium digitatum (RV 06) was previously obtained from rotten maize grains. This work aim was to optimize the production and characterize this microorganism produced cellulase. A CMCase maximum production (1.6 U/mL) was obtained in stationary liquid culture, with an initial pH of 5.0, at 25 °C, with 1% lactose as carbon source, and cultured for 5 days. The produced enzyme was purified by ammonium sulfate precipitation and exclusion chromatography. The purified enzyme optimal temperature and pH were 60 °C and 5.2, respectively. The experimental T_m of thermal inactivation was 63.68 °C, and full activity was recovered after incubation of 7 h at 50 °C. The purified 74 kDa CMCase presented K_M for CMC of 11.2 mg/mL, V_max of 0.13 μmol/min, k_cat of 52 s^-1, and k_cat/K_M of 4.7 (mg/mL)^-1 s^-1. The purified enzyme had a high specificity for CMC and p-nitrophenyl cellobioside and released glucose and cellobiose as final products of the CMC hydrolysis. The enzyme trypsin digestion produced peptides whose masses were obtained by MALDI-TOF/TOF mass spectrometry, which was also used to obtain two peptide sequences. These peptide sequences and the mass peak profile retrieved a CBHI within the annotated genome of P. digitatum PD1. Sequence alignments and phylogenetic analysis confirmed this enzyme as a CBHI of the glycoside hydrolase family 7. The P. digitatum PD1 protein in silico structural model revealed a coil and β-conformation predominance, which was confirmed by circular dichroism of the P. digitatum RV 06 purified enzyme.

A Neutral Thermostable β-1,4-Glucanase from Humicola insolens Y1 with Potential for Applications in Various Industries

We cloned a new glycoside hydrolase family 6 gene, Hicel6C, from the thermophilic fungus Humicola insolens Y1 and expressed it in Pichia pastoris. Using barley β-glucan as a substrate, recombinant HiCel6C protein exhibited neutral pH (6.5) and high temperature (70°C) optima. Distinct from most reported acidic fungal endo-β-1,4-glucanases, HiCel6C was alkali-tolerant, retaining greater than 98.0, 61.2, and 27.6% of peak activity at pH 8.0, 9.0, and 10.0, respectively, and exhibited good stability over a wide pH range (pH 5.0−11.0) and at temperatures up to 60°C. The K_m and V_max values of HiCel6C for barley β-glucan were 1.29 mg/mL and 752 μmol/min·mg, respectively. HiCel6C was strictly specific for the β-1,4-glucoside linkage exhibiting activity toward barley β-glucan, lichenan, and carboxy methylcellulose sodium salt (CMC-Na), but not toward laminarin (1,3-β-glucan). HiCel6C cleaved the internal glycosidic linkages of cellooligosaccharides randomly and thus represents an endo-cleaving enzyme. The predominant product of polysaccharide hydrolysis by HiCel6C was cellobiose, suggesting that it functions by an endo-processive mechanism. The favorable properties of HiCel6C make it a good candidate for basic research and for applications in the textile and brewing industries.

High-level expression of a novel Penicillium endo-1,3(4)-β-d-glucanase with high specific activity in Pichia pastoris

A novel endo-1,3(4)-β-d-glucanase gene (bgl16C1) from Penicillium pinophilum C1 was cloned and sequenced. The 945-bp full-length gene encoded a 315-residue polypeptide consisting of a putative signal peptide of 18 residues and a catalytic domain belonging to glycosyl hydrolase family 16. The deduced amino acid sequence showed the highest identity (82%) with the putative endo-1,3(4)-β-glucanase from Talaromyces stipitatus ATCC 10500 and 60% identity with the characterized β-1,3(4)-glucanase from Paecilomyces sp. FLH30. The gene was successfully overexpressed in Pichia pastoris. Recombinant Bgl16C1 constituted 95% of total secreted proteins (2.61 g l−1) with activity of 28,721 U ml−1 in a 15-l fermentor. The purified recombinant Bgl16C1 had higher specific activity toward barley β-glucan (12,622 U mg−1) than all known glucanases and also showed activity against lichenan and laminarin. The enzyme was optimally active at pH 5.0 and 55°C and exhibited good stability over a broad acid and alkaline pH range (&gt;85% activity at pH 3.0–7.0 and even 30% at pH 11.0). All these favorable enzymatic properties make it attractive for potential applications in various industries.

Genome walking in eukaryotes

Genome walking is a molecular procedure for the direct identification of nucleotide sequences from purified genomes. The only requirement is the availability of a known nucleotide sequence from which to start. Several genome walking methods have been developed in the last 20 years, with continuous improvements added to the first basic strategies, including the recent coupling with next generation sequencing technologies. This review focuses on the use of genome walking strategies in several aspects of the study of eukaryotic genomes. In a first part, the analysis of the numerous strategies available is reported. The technical aspects involved in genome walking are particularly intriguing, also because they represent the synthesis of the talent, the fantasy and the intelligence of several scientists. Applications in which genome walking can be employed are systematically examined in the second part of the review, showing the large potentiality of this technique, including not only the simple identification of nucleotide sequences but also the analysis of large collections of mutants obtained from the insertion of DNA of viral origin, transposons and transfer DNA (T-DNA) constructs. The enormous amount of data obtained indicates that genome walking, with its large range of applicability, multiplicity of strategies and recent developments, will continue to have much to offer for the rapid identification of unknown sequences in several fields of genomic research.