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[Display omitted] • Microarray Polymer Profiling allows high-throughput mapping of glycans in food. • Hemicellulose, starch and pectin were detected using monoclonal antibodies. • Xylan is a major component of a model Burnt-On/Baked-On (BoBo) food polymer. • Burning during cooking causes cell-wall glycan structure disintegration. • Adding CAZymes to dishwashing detergents may improve cleaning of food soils. Burning of food materials during cooking can increase the difficulty in removal from solid surfaces, forming residual food soils. Using molecular probe-based technologies, the aim of this work was to elucidate the composition and relative abundance of glycans within a Burnt-On/Baked-On (BoBo) model food soil and investigate enzyme systems that may facilitate soil breakdown. Microarray Polymer Profiling identified xylan, arabinoxylan, mixed-linkage glucan and mannan as target substrates for the enzymatic cleaning of BoBo residues from surfaces. Indirect immunofluorescence microscopy revealed that burning resulted in extensive structural modifications and degradation of the three-dimensional architecture of constituent polysaccharide matrices. Results from high-throughput enzyme screening indicate that inclusion of xylan depolymerising enzymes in automatic dishwashing detergents may improve cleaning of recalcitrant, plant glycan-rich BoBo soils. Collectively, this study provides new insight into the composition and removal chemistry of complex, multi-component food soils. [ABSTRACT FROM AUTHOR]

Glycans are major nutrients available to the human gut microbiota. The Bacteroides are generalist glycan degraders, and this function is mediated largely by polysaccharide utilization loci (PULs). The genomes of several Bacteroides species contain a PUL, PUL1,6-β-glucan, that was predicted to target mixed linked plant 1,3;1,4-β-glucans. To test this hypothesis we characterized the proteins encoded by this locus in Bacteroides thetaiotaomicron, a member of the human gut microbiota. We show here that PUL1,6-β-glucan does not orchestrate the degradation of a plant polysaccharide but targets a fungal cell wall glycan, 1,6-β-glucan, which is a growth substrate for the bacterium. The locus is up-regulated by 1,6-β-glucan and encodes two enzymes, a surface endo-1,6-β-glucanase, BT3312, and a periplasmic β-glucosidase that targets primarily 1,6-β-glucans. The non-catalytic proteins encoded byPUL1,6-β-glucan target 1,6-β-glucans and comprise a surface glycan-binding protein and a SusD homologue that delivers glycans to the outer membrane transporter. We identified the central role of the endo-1,6-β-glucanase in 1,6-β-glucan depolymerization by deleting bt3312, which prevented the growth of B. thetaiotaomicron on 1,6-β-glucan. The crystal structure of BT3312 in complex with β-glucosyl-1,6-deoxynojirimycin revealed a TIM barrel catalytic domain that contains a deep substrate-binding cleft tailored to accommodate the hook-like structure adopted by 1,6-β-glucan. Specificity is driven by the complementarity of the enzyme active site cleft and the conformation of the substrate. We also noted that PUL1,6-β-glucan is syntenic to many PULs from other Bacteroidetes, suggesting that utilization of yeast and fungal cell wall 1,6-β-glucans is a widespread adaptation within the human microbiota. [ABSTRACT FROM AUTHOR]

The large bowel microbiota, a complex ecosystem resident within the gastrointestinal tract of all human beings and large mammals, functions as an essential, nonsomatic metabolic organ, hydrolysing complex dietary polysaccharides and modulating the host immune system to adequately tolerate ingested antigens. A significant member of this community, Bacteroides thetaiotaomicron, has evolved a complex system for sensing and processing a wide variety of natural glycoproducts in such a way as to provide maximum benefit to itself, the wider microbial community and the host. The immense ability of B. thetaiotaomicron as a `glycan specialist' resides in its enormous array of carbohydrate-active enzymes, many of which are arranged into polysaccharide-utilization loci (PULs) that are able to degrade sugar polymers that are often inaccessible to other gut residents, notably α-mannan. The B. thetaiotaomicron genome encodes ten putative α-mannanases spread across various PULs; however, little is known about the activity of these enzymes or the wider implications of α-mannan metabolism for the health of both the microbiota and the host. In this study, SAD phasing of a selenomethionine derivative has been used to investigate the structure of one such B. thetaiotaomicron enzyme, BT2949, which belongs to the GH76 family of α-mannanases. BT2949 presents a classical (α/α)6-barrel structure comprising a large extended surface cleft common to other GH76 family members. Analysis of the structure in conjunction with sequence alignments reveals the likely location of the catalytic active site of this noncanonical GH76. [ABSTRACT FROM AUTHOR]