Enzymatic characterization of heterologously expressed fungal β-glucosidase BGLII in Escherichia coli

Saprophytic filamentous fungi such as Trichoderma sp. are capable of producing three categories of cellulase for cellulose degradation into glucose; endoglucanase, cellobiohydrolase and β-glucosidase. Trichoderma reesei in particular has an extensively studied cellulase enzyme system, establishing it as a model organism for enzymatic production. Studies on β-glucosidases produced by Trichoderma sp. have elucidated two variants, which have been classified into glycosyl hydrolase families 1 and 3, both including retaining enzymes capable of substrate hydrolysis via double-displacement method with retention of anomeric carbon. Extensive studies on BglI enzyme isolated has been compared and found to have sequence similarity to other known glycosyl hydrolase family 3 β-glucosidases, an enzyme that is cell wall bound or expressed extracellularly, affects rate of reducing sugar formation from cellulase and involved in synthesis of soluble inducer of cellulolytic enzymes. Comparatively, enzyme characterization of the second β-glucosidase, BglII, has been relatively recent. Nevertheless, it has been identified to be expressed intracellularly, has high affinity and catalyzes transglycosylation reactions on cellobiose. Of particular interest, BglII has shown lower sensitivity to glucose inhibition, an appealing character for bioprocess development for efficient lignocellulosic biomass saccharification. As such, using local Trichoderma sp., this study has sought to characterize the BglII gene isolated and following heterologous expression in Escherichia coli, characterize the recombinant enzyme for enzyme activity, glucose tolerance and product synthesis

Pengoptimuman campuran enzim selulase rekombinan untuk penguraian tandan kosong kelapa sawit

Penggunaan enzim selulase untuk penguraian biojisim pertanian lignoselulosa telah lama dikaji dan pelbagai usaha telah dilakukan untuk meningkatkan kecekapan proses hidrolisis. Keberkesanan penguraian biojisim pertanian kepada gula ringkas memerlukan satu campuran enzim yang mengandungi pelbagai jenis aktiviti selulolitik. Dalam kajian ini, satu campuran multi-enzim rekombinan yang terdiri daripada tiga komponen asas selulase iaitu endoglukanase (EglB) dan β-glukosidase (BglA) daripada Aspergillus niger serta selobiohidrolase (CbhII) daripada Trichoderma virens telah dibentuk khusus untuk hidrolisis tandan kosong kelapa sawit (TKKS). Penghasilan enzim selulase rekombinan telah dilakukan menggunakan hos pengekspresan Pichia pastoris. Pengoptimuman nisbah enzim untuk tindak balas ditentukan menggunakan Kaedah Gerak Balas Permukaan (RSM). Hasil menunjukkan hidrolisis TKKS pada suhu 50 °C dan pH 5.0 menggunakan enzim pada nisbah 641.4 unit CMCase: 10.14 unit Avicelase: 93.8 unit β-glukosidase, menghasilkan gula terturun dan glukosa tertinggi, masing-masing sebanyak 63 mg dan 40 mg per gram substrat TKKS. Hasil hidrolisis TKKS oleh campuran multi enzim yang telah dibentuk dalam kajian ini menunjukkan ketiga-tiga gabungan enzim rekombinan ini berpotensi untuk digunakan bagi penguraian TKKS

Optimising cutinase enzyme recovery in thermo-induced phase separation of LS54/DX ATPS by enhanced volume exclusion effect

Low recovery of cutinase enzyme in water-enriched phase after thermo-induced separation stage of LS54/Dx aqueous two-phase system was improved by enhanced volume exclusion effect in the polymer-water extraction system. It was done by increased the polymer concentration in the polymer-water system. After primary phase separation, more LS54 (polymer) which is the system’s component itself were added into polymer-enriched phase and mixed thoroughly before thermo-induced separation step proceeded. The compositions of LS54 added into the polymer-enriched phase were 0.25, 0.5 and 0.75 g LS54/g top phase. The thermo-induced phase separation was carried out at 37°C. It was found that cutinase recovery in water-enriched phase was increased up to 5-13% with the increment of polymer concentration in the system as compared to a system without polymer addition. The optimum concentration obtained for the polymer added was 0.5 g LS54/g top phase whereby it attained 82% recovery of cutinase enzyme in water-enriched phase after thermoseparation step. Although the increment of enzyme recovery was not exceptionally high as compared to another method such as adding ligand, an affinity tag or neutral salt, still this method is applicable because of its more straightforward work, polymer recycle capability, and enzyme recovery in water phase would definitely give benefit to further downstream processing

In silico structural characterization of L. lactis subsp. cremoris MG1363 Ffh-Ftsy complex in protein targeting interaction

In bacteria, gene conservation and experimental data show that Lactococcus lactis has the simplest version of protein secretion system compared to Escherichia coli and Bacillus subtilis whose systems are more complex. L. lactis only possess the signal recognition particle (SRP) pathway, where the specific interaction of Ffh and FtsY is known to be essential for the efficiency and fidelity of its protein targeting. Therefore, modelling and structural characterization study of Ffh and FtsY will give an idea of its crucial region and amino acids that are critical in Ffh-FtsY interaction during protein targeting. This work is the first attempt to model L. lactis Ffh-FtsY complex, which was derived by computational docking, where a blind dock was applied. Results showed that the complex interface was predominantly stabilized by four hydrophobic interactions and 17 hydrogen bonds, where these putative binding interfaces are mostly confined at the motifs II and III in each G domain of Ffh and FtsY. Several residues were expected to play important roles in initiating or regulating guanosine triphosphate hydrolysis, including residue R142. This structural information will allow for the rational design of L. lactis Ffh-FtsY association in the future

Effect of Various Cultivation Methods on Cellobiohydrolase Production from Aspergillus niger

Three different cultivation methods, i.e., shaking-flask culture (SFC), static surface liquid culture (SSLC) and membrane surface liquid culture (MSLC) were used to cultivate the filamentous fungi,  Aspergillus niger PY11 in order to differentiate its behaviours by different cultivation methods using the same media, by determination of growth profile during fermentation. The dry cell weight, protein concentration, cellobiohydrolase (CBH) activity and residual sugar concentration in SSLC and MSLC were 1.5 to 2-folds than that by SFC. Cultivation of A. niger using MSLC was higher than SSLC with maximum biomass concentration, protein concentration and enzyme activity were 0.93 g dry weight/ml medium, 3.49 mg/ml and 36.99 U/ml respectively. MSLC possess the best growth characteristics and was the best cultivation method in production of CBH from A. niger PY11

Inactivation of the Catalytic Subunit of cAMP-Dependent Protein Kinase A Causes Delayed Appressorium Formation and Reduced Pathogenicity of Colletotrichum gloeosporioides

The cyclic AMP- (cAMP-) dependent protein kinase A signaling pathway is one of the major signaling pathways responsible for regulation of the morphogenesis and pathogenesis of several pathogenic fungi. To evaluate the role of this pathway in the plant pathogenic fungus, Colletotrichum gloeosporioides, the gene encoding the catalytic subunit of cAMP-dependent protein kinase A, CgPKAC, was cloned, inactivated, and the mutant was analyzed. Analysis of the Cgpkac mutant generated via gene replacement showed that the mutants were able to form appressoria; however, their formation was delayed compared to the wild type. In addition, the mutant conidia underwent bipolar germination after appressoria formation, but no appressoria were generated from the second germ tube. The mutants also showed reduced ability to adhere to a hydrophobic surface and to degrade lipids localized in the appressoria. Based on the number of lesions produced during a pathogenicity test, the mutant's ability to cause disease in healthy mango fruits was reduced, which may be due to failure to penetrate into the fruit. These findings indicate that cAMP-dependent protein kinase A has an important role in regulating morphogenesis and is required for pathogenicity of C. gloeosporioides

Profil pengekspresan gen mengekod delta 6 dan delta 12-asid lemak desaturase Cunninghamella bainieri semasa biosintesis asid gamma-linolenik

Delta 6-asid lemak desaturase dan delta 12-asid lemak desaturase merupakan enzim yang diperlukan bagi langkah desaturasi semasa proses biosintesis asid gamma-linolenik (GLA) oleh kulat oleaginus. Objektif kajian ini ialah untuk menganalisis profil pengekspresan gen mengekod enzim delta 6-asid lemak desaturase (des6) dan delta 12-asid lemak desaturase (des12) kulat oleaginus Cunninghamella bainieri semasa penghasilan GLA. Jujukan gen separa bersaiz 1372 pb bagi des6 dan 1008 pb bagi des12 telah dipencil daripada C. bainieri. Analisis pengekspresan gen menggunakan kaedah tindak balas berantai polimerase kuantitatif masa sebenar (RT-qPCR) menunjukkan perubahan kadar pengekspresan des6 adalah lebih tinggi berbanding kadar pengekspresan des12 semasa penghasilan GLA. Pengekspresan des6 adalah tertinggi selepas 24 jam dikultur dalam medium penghasilan GLA. Namun, kadar pengekspresannya menurun hingga jam ke-96 pertumbuhan tetapi meningkat semula pada jam ke-120. Bagi des12, kadar pengekspresannya adalah lebih sekata dengan pengekspresan tertinggi dikesan pada jam ke-120. Analisis penghasilan GLA menunjukkan jumlah GLA dalam sel berkolerasi dengan kadar pengekspresan des6. Hasil kajian mencadangkan bahawa aras pengekspresan des6 adalah penting dalam menentukan aras GLA dalam C. bainieri

Cloning, heterologous expression and characterisation of a recombinant cellobiohydrolase from Humicola insolens ATCC16454 in Pichia pastoris

A cellobiohydrolase gene from the thermophilic fungus Humicola insolens ATCC 16454 was expressed in the methylotrophic yeast Pichia pastoris X-33, and the biochemical properties of the recombinant protein were characterised. The full-length cDNA of the cellobiohydrolase gene avi2 was cloned into the P. pastoris expression vector pPICZαC and expressed extracellularly as a recombinant cellobiohydrolase protein with a molecular weight of approximately 52.3 kDa. The purified recombinant Avi2 enzyme displayed an optimal activity at 50°C and was found stable between temperatures of 30°C and 60°C. The optimal pH of the enzyme was pH 5.0. More than 80% of the enzyme activity was retained at pH values ranging from pH3.0 to pH9.0. Recombinant Avi2 enzyme showed its highest activity towards the substrates Avicel (0.075 U mg-1) and Sigmacell-cellulose (0.018 U mg-1). Very low or undetectable hydrolysis was observed with cellobiose and filter paper. Metal ions, such as Mn2+, Co2+, and Ba2+, increased the activity of the recombinant enzyme. Manganese ions caused the highest increase in activity of approximately 1.38-fold compared to the control assay. Other ions such as Pd2+, Cu2+, Zn2+, Fe2+, and SDS, however, inhibited Avi2 enzyme activity. Interestingly, this recombinant enzyme showed high pH stability when it was incubated in either acidic or basic solutions

In-silico characterization of glycosyl hydrolase family 1 β glucosidase from Trichoderma asperellum UPM1

β-glucosidases (Bgl) are widely utilized for releasing non-reducing terminal glucosyl residues. Nevertheless, feedback inhibition by glucose end product has limited its application. A noticeable exception has been found for β-glucosidases of the glycoside hydrolase (GH) family 1, which exhibit tolerance and even stimulation by glucose. In this study, using local isolate Trichoderma asperellum UPM1, the gene encoding β-glucosidase from GH family 1, hereafter designated as TaBgl2, was isolated and characterized via in-silico analyses. A comparison of enzyme activity was subsequently made by heterologous expression in Escherichia coli BL21(DE3). The presence of N-terminal signature, cis-peptide bonds, conserved active site motifs, non-proline cis peptide bonds, substrate binding, and a lone conserved stabilizing tryptophan (W) residue confirms the identity of Trichoderma sp. GH family 1 β-glucosidase isolated. Glucose tolerance was suggested by the presence of 14 of 22 known consensus residues, along with corresponding residues L167 and P172, crucial in the retention of the active site’s narrow cavity. Retention of 40% of relative hydrolytic activity on ρ-nitrophenyl-β-D-glucopyranoside (ρNPG) in a concentration of 0.2 M glucose was comparable to that of GH family 1 β-glucosidase (Cel1A) from Trichoderma reesei. This research thus underlines the potential in the prediction of enzymatic function, and of industrial importance, glucose tolerance of family 1 β-glucosidases following relevant in-silico analyses