Structural characterization of oligosaccharide from Spirulina platensis and its effect on the faecal microbiota in vitro

In the present study,an oligosaccharide SPO-1 from Spirulina platensis was prepared by glycosidase from a marine bacterium.The prebiotic activity of SPO-1 on the growth of Lactobacillus paracasei and Bifidobacterium animalis,and its effect on human gut microbiota were examined in vitro.The molecular weight of the tetrasaccharide SPO-1 was 650.2 Da,and it was mainly composed of glucose with α-type glycosidic linkages.The prebiotic activity score of SPO-1 was the highest for the growth of probiotic strains L.paracasei and B.animalis.Furthermore,as fermentation proceeded,SPO-1 was gradually degraded and utilized by intestinal bacteria.The results showed that after treatment with SPO-1,carbohydrate consumption and short-chain fatty acids levels were increased,especially those of i-butyric and i-valeric acids.Moreover,SPO-1 significantly promoted the abundance,diversity and composition of gut microbiota,especially stimulating the growth of Bacteroides,Escherichia-Shigella and Megamonas.In addition,the change in intestinal microbiota function predicted by phylogenetic investigation of communities by reconstruction of unobserved states(PICRUSt)after treatment with SPO-1 is mainly related to the terms“carbohydrate metabolism”and“amino acid metabolism”.These results suggest that SPO-1 is a potential oligosaccharide in regulation of intestinal microbiota.

Recycling of waste aluminum scraps to fabricate sulfidated zero-valent iron-aluminum particles for enhanced chromate removal

Massive waste aluminum scraps produced from the spent aluminum products have high electron capacity and can be recycled as an attractive alternative to materials based on zerovalent iron(Fe^(0))for the removal of oxidative contaminants from wastewater.This study thus proposed an approach to fabricate micron-sized sulfidated zero-valent iron-aluminum particles(S-Al^(0)@Fe^(0))with high reactivity,electron selectivity and capacity using recycled waste aluminum scraps.S-Al^(0)@Fe^(0)with a three-layer structure contained zero-valent aluminum(Al^(0))core,Fe^(0) middle layer and iron sulfide(FeS)shell.The rates of chromate(Cr(Ⅵ))removal by S-Al^(0)@Fe^(0)at pH 5.0-9.0 were 1.6-5.9 times greater than that by sulfidated zero-valent iron(S-Fe^(0)).The Cr(Ⅵ)removal capacity of S-Al^(0)@Fe^(0)was 8.2-,11.3-and 46.9-fold greater than those of S-Fe0,zero-valent iron-aluminum(Al^(0)-Fe^(0))and Fe^(0),respectively.The chemical cost of S-Al^(0)@Fe^(0) for the equivalent Cr(Ⅵ)removal was 78.5%lower than that of S-Fe^(0).Negligible release of soluble aluminum during the Cr(Ⅵ)removal was observed.The significant enhancement in the reactivity and capacity of S-Al^(0)@Fe^(0)was partially ascribed to the higher reactivity and electron density of the Al0core than Fe^(0).More importantly,S-Al^(0)@Fe^(0) served as an electric cell to harness the persistent and selective electron transfer from the Al^(0)-Fe^(0) core to Cr(Ⅵ)at the surface via coupling Fe^(0)-Fe^(2+)-Fe^(3+)redox cycles,resulting in a higher electron utilization efficiency.Therefore,S-Al^(0)@Fe^(0) fabricated using recycled waste aluminum scraps can be a cost-effective and environmentally-friendly alternative to S-Fe^(0) for the enhanced removal of oxidative contaminants in industrial wastewater.

A RETROSPECTIVE TRUST REGION ALGORITHM WITH TRUST REGION CONVERGING TO ZERO

We propose a retrospective trust region algorithm with the trust region converging to zero for the unconstrained optimization problem. Unlike traditional trust region algo- rithms, the algorithm updates the trust region radius according to the retrospective ratio, which uses the most recent model information. We show that the algorithm preserves the global convergence of traditional trust region algorithms. The superlinear convergence is also proved under some suitable conditions.