Cloning and Expression of a Novel GH134 β-Mannanase Gene from Thermophilic Fungus Rhizopus microsporus and Its Application in Juice Processing

A thermophilic fungus, named HBFH10, was isolated from Luzhou-flavor Daqu and identified as Rhizopus microsporus. A new β-mannanase gene (RmMan134) from Rhizopus microsporus HBHF10, was cloned using degenerate primers, expressed, and characterized. The cloned RmMan134 gene had a total length of 552 bp without introns, encoding 183 amino acids and one stop codon. The expressed enzyme was composed of one signal peptide sequence of 19 amino acid residues and the catalytic region of the GH134 family. The optimal pH and temperature for the recombinant enzyme were 6.0 and 50 ℃, respectively. It had high thermal and pH stability. Its molecular mass was estimated to be approximately 18.5 kDa, and it was a glycosylated molecule. When konjac gum was used as the substrate, the Km and Vmax values of RmMan134 were 0.66 mg/mL and 57.1 μmol/(min·mg), respectively. RmMan134 exhibited the best clarification efficiency for orange juice, resulting in a 23.8% increase in its clarity, followed apple juice (11%) and peach juice (7%). Moreover, RmMan134 significantly increased the yield of grape juice by about 7%. Overall, RmMan134 has good application prospects in juice processing

Characterization of a Novel Thermophilic Mannanase and Synergistic Hydrolysis of Galactomannan Combined with Swollenin

Aspergillus fumigatus HBFH5 is a thermophilic fungus which can efficiently degrade lignocellulose and which produces a variety of glycoside hydrolase. In the present study, a novel β-mannanase gene (AfMan5A) was expressed in Pichia pastoris and characterized. AfMan5A is composed of 373 amino acids residues, and has a calculated molecular weight of 40 kDa. It has been observed that the amino acid sequence of AfMan5A showed 74.4% homology with the ManBK from Aspergillus niger. In addition, the recombined AfMan5A exhibited optimal hydrolytic activity at 60 °C and pH 6.0. It had no activity loss after incubation for 1h at 60 °C, while 65% of the initial activity was observed after 1 h at 70 °C. Additionally, it maintained about 80% of its activity in the pH range from 3.0 to 9.0. When carob bean gum was used as the substrate, the Km and Vmax values of AfMan5A were 0.21 ± 0.05 mg·mL−1 and 15.22 ± 0.33 U mg−1·min−1, respectively. AfMan5A and AfSwol showed a strong synergistic interaction on galactomannan degradation, increasing the reduction of the sugars by up to 31%. Therefore, these findings contribute to new strategies for improving the hydrolysis of galactomannan using the enzyme cocktail

A Thermophilic GH5 Endoglucanase from Aspergillus fumigatus and Its Synergistic Hydrolysis of Mannan-Containing Polysaccharides

In this study, we isolated and identified a thermophilic strain of Aspergillus fumigatus from the “Daqu” samples. Transcriptomic analysis of A. fumigatus identified 239 carbohydrate-active enzymes (CAZy)-encoding genes, including 167 glycoside hydrolase (GH)-encoding genes, 58 glycosyltransferase (GT)-encoding genes, 2 polysaccharide lyase (PLs)-encoding genes and 12 carbohydrate esterase (CEs)-encoding genes, which indicates that the strain has a strong potential for application for enzyme production. Furthermore, we also identified a novel endoglucanase gene (AfCel5A), which was expressed in Pichia pastoris and characterized. The novel endoglucanase AfCel5A exhibited the highest hydrolytic activity against CMC-Na and the optimal activity at 80 °C and pH 4.0 and also showed good stability at pH 3.0–11.0 and below 70 °C. The Km and Vmax values of AfCel5 were 0.16 ± 0.05 mg·mL−1 and 7.23 ± 0.33 mol mg−1·min−1, respectively, using CMC-Na as a substrate. Further, the endoglucanase exhibited a high tolerance toward NaCl as well as glucose. In addition, the finding that the endoglucanase AfCel5A in combination with β-mannanse (ManBK) clearly increased the release of total reducing sugars of glucomannan by up to 74% is significant

High-Efficiency Selective Electron Tunnelling in a Heterostructure Photovoltaic Diode

A heterostructure photovoltaic diode featuring an all-solid-state TiO₂/graphene/dye ternary interface with high-efficiency photogenerated charge separation/transport is described here. Light absorption is accomplished by dye molecules deposited on the outside surface of graphene as photoreceptors to produce photoexcited electron–hole pairs. Unlike conventional photovoltaic conversion, in this heterostructure both photoexcited electrons and holes tunnel along the same direction into graphene, but only electrons display efficient ballistic transport toward the TiO₂ transport layer, thus leading to effective photon-to-electricity conversion. On the basis of this ipsilateral selective electron tunnelling (ISET) mechanism, a model monolayer photovoltaic device (PVD) possessing a TiO₂/graphene/acridine orange ternary interface showed ∼86.8% interfacial separation/collection efficiency, which guaranteed an ultrahigh absorbed photon-to-current efficiency (APCE, ∼80%). Such an ISET-based PVD may become a fundamental device architecture for photovoltaic solar cells, photoelectric detectors, and other novel optoelectronic applications with obvious advantages, such as high efficiency, easy fabrication, scalability, and universal availability of cost-effective materials