Bo Feng,Jinxiu Peng,Wenpu Zhang,Xianghan Ning,Yutao Guo,Wencai Zhang
In the flotation separation of chalcopyrite and talc, depressants are usually added to selectively prevent talc from floating. Commonly used depressants lack selectivity, resulting in the depression of both talc and sulfide minerals. To solve this problem, the role of locust bean gum in the flotation separation of chalcopyrite and talc was studied and its mechanism of talc depression discussed. Single mineral flotation test results showed that both chalcopyrite and talc were floatable in the tested pH range of 3–11 and that locust bean gum depressed the flotation of both minerals; however, locust bean gum showed a strong depressing effect on talc in the pH range of 5–9 at a dosage of 2000 g/t. The results of flotation tests performed on mixed minerals indicated that the use of locust bean gum as a depressant can achieve flotation separation of chalcopyrite from talc. A concentrate of 30.1% Cu was achieved at 88.1% recovery from a feed material containing 15.2% Cu. This was attributed to greater adsorption of locust bean gum on the surface of talc compared with that on the chalcopyrite. Zeta potential and X-ray photoelectron spectroscopy measurements showed that the locust bean gum adsorbed on talc mainly through physical interactions; hydrophobic interactions were considered the main driving force and hydrogen bonds also played a role.
Hongmei Zhang,Ying Wang,Yanqing Wang,Shixin Sun,Jian Cao
In the present work, we have studied the structure and thermal stability of bovine serum albumin (BSA)-locust bean gum (LBG) mixture. It was found from the spectral results that the presence of LBG resulted in slightly decreasing the α–helical content and the partly unfolding of the skeleton of BSA. LBG binds to the neighboring amino acids of Trp and partly disturbs the microenvironment around Trp residues of BSA. The molecular docking confirms that there are more than one possible binding sites to bind with LBG by multi non-covalent forces. During the thermal unfolding process, LBG led to increase the secondary structure stability of protein by assembling each other. In addition, BSA even has good reversibility of the unfolding process in the presence of LBG promoting the thermal-induced tertiary structural degeneration of BSA. Collectively, our results provide evidence that LBG induces some behavior changes of BSA.
In this study, an acidophilic GH5 β-mannanase (TaMan5) from Trichoderma asperellum ND-1 was efficiently expressed in Pichia pastoris (a 2.0-fold increase, 67.5 ± 1.95 U/mL). TaMan5 displayed the highest specificity toward locust bean gum (Km = 1.34 mg/mL, Vmax = 749.14 μmol/min/mg) at pH 4.0 and 65°C. Furthermore, TaMan5 displayed remarkable tolerance to acidic environments, retaining over 80% of its original activity at pH 3.0–5.0. The activity of TaMan5 was remarkably decreased by Cu2+, Mn2+, and SDS, while Fe2+/Fe3+ improved the enzyme activity. A thin-layer chromatography (TLC) analysis of the action model showed that TaMan5 could rapidly degrade mannan/MOS into mannobiose without mannose via hydrolysis action as well as transglycosylation. Site-directed mutagenesis results suggested that Glu205, Glu313, and Asp357 of TaMan5 are crucial catalytic residues, with Asp152 playing an auxiliary function. Additionally, TaMan5 and commercial α-galactosidase displayed a remarkable synergistic effect on the degradation of galactomannans. This study provided a novel β-mannanase with ideal characteristics and can be considered a potential candidate for the production of bioactive polysaccharide mannobiose.
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