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

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

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

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

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

Functional Analysis of an Appressorium-Specific Gene from Colletotrichum gloeosporioides

A novel gene (CAS2) specifically expressed during appressorium formation was isolated from Colletotrichum gloeosporioides using Differential Display RT-PCR. CAS2 comprises 368 deduced amino acid residues and is 50% identical to a hypothetical protein from Chaetomium globosum. ProtFun 2.2 server analysis predicted that Cas2 functions as a transport and binding protein. Based on putative transmembrane domain prediction software (HMMTOP), Cas2 protein is composed of five alpha-helical transmembrane domains with a very short external N-terminus tail and long internal C-terminus. ExPASy ScanProsite analysis showed the presence of integrin beta chain cysteine-rich domain, N-myristoylation site, EGF-like domain, 2Fe-2S ferredoxins, iron-sulfur binding region, VWFC domain, fungal hydrophobins signature, membrane lipoprotein lipid attachment site, and Janus-faced atracotoxin (J-ACTX) family signature in CAS2 protein. Mutants with deleted CAS2 were not significantly different in terms of vegetative growth, conidiation, and appressoria production compared to wild type. However, the Cas2 mutant produced multipolar germination, a feature which distinguishes it from wild type strain. Interestingly, the mutant is non-virulent to mango fruits, indicating that CAS2 may encode proteins that function as novel virulence factors in fungal pathogens

Enhanced secretory production of hemolysin-mediated cyclodextrin-glucanotransferase in Escherichia coli by random mutagenesis of the ABC transporter system.

The hemolysin transport system was found to mediate the release of cyclodextrin glucanotransferase (CGTase) into the extracellular medium when it was fused to the C-terminal 61 amino acids of HlyA (HlyAs(61)). To produce an improved-secretion variant, the hly components (hlyAs, hlyB and hlyD) were engineered by directed evolution using error-prone PCR. Hly mutants were screened on solid LB-starch plate for halo zone larger than the parent strain. Through screening of about 1 × 10(4) Escherichia coli BL21(DE3) transformants, we succeeded in isolating five mutants that showed a 35-217% increase in the secretion level of CGTase-HlyAs(61) relative to the wild-type strain. The mutation sites of each mutant were located at HlyB, primarily along the transmembrane domain, implying that the corresponding region was important for the improved secretion of the target protein. In this study we describe the finding of novel site(s) of HlyB responsible for enhancing secretion of CGTase in E. coli