Enzymatic preparation of manno-oligosaccharides from locust bean gum and palm kernel cake, and investigations into its prebiotic activity

BACKGROUND: Manno-oligosaccharides (MOS) is known as a kind of prebiotics. Mannanase plays a key role for the degradation of mannan to produce MOS. In this study, the mannanases of glycoside hydrolase (GH) families 5 Man5HJ14 and GH26 ManAJB13 were employed to prepare MOS from locust bean gum (LBG) and palm kernel cake (PKC). The prebiotic activity and utilization of MOS were assessed in vitro using the probiotic Lactobacillus plantarum strain. RESULTS: Galactomannan from LBG was converted to MOS ranging in size from mannose up to mannoheptose by Man5HJ14 and ManAJB13. Mannoheptose was got from the hydrolysates produced by Man5HJ14, which mannohexaose was obtained from LBG hydrolyzed by ManAJB13. However, the same components of MOS ranging in size from mannose up to mannotetrose were observed between PKC hydrolyzed by the mannanases mentioned above. MOS stability was not affected by high-temperature and high-pressure condition at their natural pH. Based on in vitro growth study, all MOS from LBG and PKC was effective in promoting the growth of L. plantarum CICC 24202, with the strain preferring to use mannose to mannotriose, rather than above mannotetrose. CONCLUSIONS: The effect of mannanases and mannan difference on MOS composition was studied. All of MOS hydrolysates showed the stability in adversity condition and prebiotic activity of L. plantarum, which would have potential application in the biotechnological applications.

Effect of exogenous phytohormones treatment on glycyrrhizic acid accumulation and preliminary exploration of the chemical control network based on glycyrrhizic acid in root of Glycyrrhiza uralensis

ABSTRACT One-year-old Glycyrrhiza uralensis Fisch. ex DC, Fabaceae, was treated with three exogenous phytohormones in June and July, namely gibberellin, auxin (indole-3-acetic acid), methyl jasmonate at different concentrations. Control plants were treated with water. Roots of controls and hormones-treated G. uralensis plants were harvested at different times, and the contents of seven main chemical components were determined. Root glycyrrhizic acid content of plants treated in June increased significantly compared with controls, and the difference was significant. As for plants treated in July, root glycyrrhizic acid content increased in which sprayed with appropriate concentrations of hormones, but the effects of hormones were more evident in plants treated in June coincided with the vigorous growth period than those treated in July. Gibberellin at 40 mg/l and auxin at 40 mg/l applied in the two treatment periods significantly promoted the accumulation of glycyrrhizic acid in G. uralensis root. Treatment with methyl jasmonate at 100 and 25 mg/l in June and July, respectively, also increased glycyrrhizic acid content significantly. The determination of major active compositions indicated that liquiritin, isoliquiritin, isoliquiritin apioside and liquiritin apioside contents were positively related to glycyrrhizic acid content. The study preliminarily found phytohormones and the main chemical components associated with glycyrrhizic acid content, and these discoveries could provide a basis for establishing a chemical control network with glycyrrhizic acid as the core, confirming the secondary product metabolic pathways in the network and completely uncovering synthesis mechanism underlying glycyrrhizic acid-combined functional gene polymorphism.