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Gluco‐oligosaccharides (GlcOS) are potential prebiotics that positively modulate beneficial gut commensals like lactobacilli. For the rational design of GlcOS as prebiotics or combined with lactobacilli as synbiotics, it is important to establish the structure requirements of GlcOS and specificity toward lactobacilli. Herein, the utilization of 10 GlcOS with varied degrees of polymerization (DP) and glycosidic linkages by 7 lactobacilli strains (Levilactobacillus brevis ATCC 8287, Limosilactobacillus reuteri ATCC PTA 6475, Lacticaseibacillus rhamnosus ATCC 53103, Lentilactobacillus buchneri ATCC 4005, Limosilactobacillus fermentum FUA 3589, Lactiplantibacillus plantarum WCFS1, and Lactobacillus gasseri ATCC 33323) was studied. L. brevis ATCC 8287 was the only strain that grew on α/β‐(1→4/6) linked disaccharides, whereas other strains showed diverse patterns, dependent on the availability of genes encoding sugar transporters and catabolic enzymes. The effect of DP on GlcOS utilization was strain dependent. β‐(1→4) Linked cello‐oligosaccharides (COS) supported the growth of L. brevis ATCC 8287 and L. plantarum WCFS1, and shorter COS (DP 2–3) were preferentially utilized over longer COS (DP 4–7) (consumption ≥90% vs. 40%–60%). α‐(1→4) Linked maltotriose and maltodextrin (DP 2–11) were effectively utilized by L. brevis ATCC 8287, L. reuteri ATCC 6475, and L. plantarum WCFS1, but not L. fermentum FUA 3589. Growth of L. brevis ATCC 8287 on branched isomalto‐oligosaccharides (DP 2–6) suggested preferential consumption of DP 2–3, but no preference between α‐(1→6) and α‐(1→4) linkages. The knowledge of the structure‐specific GlcOS utilization by different lactobacilli from this study helps the structural rationale of GlcOS for prebiotic development. [ABSTRACT FROM AUTHOR]

Prebiotics have long been used to modulate the gut microbiota and improve host health. Most established prebiotics are nondigestible carbohydrates, especially short‐chain oligosaccharides. Recently, gluco‐oligosaccharides (GlcOS) with 2–10 glucose residues and one or more O‐glycosidic linkage(s) have been found to exert prebiotic potentials (not fully established prebiotics) because of their selective fermentation by beneficial gut bacteria. However, the prebiotic effects (non‐digestibility, selective fermentability, and potential health effects) of GlcOS are highly variable due to their complex structure originating from different synthesis processes. The relationship between GlcOS structure and their potential prebiotic effects has not been fully understood. To date, a comprehensive summary of the knowledge of GlcOS is still missing. Therefore, this review provides an overview of GlcOS as potential prebiotics, covering their synthesis, purification, structural characterization, and prebiotic effect evaluation. First, GlcOS with different structures are introduced. Then, the enzymatic and chemical processes for GlcOS synthesis are critically reviewed, including reaction mechanisms, substrates, catalysts, the structures of resultant GlcOS, and the synthetic performance (yield and selectivity). Industrial separation techniques for GlcOS purification and structural characterization methods are discussed in detail. Finally, in vitro and in vivo studies to evaluate the non‐digestibility, selective fermentability, and associated health effects of different GlcOS are extensively reviewed with a special focus on the GlcOS structure–function relationship. [ABSTRACT FROM AUTHOR]

Solid acids as heterogeneous catalysts for cellulose hydrolysis have drawn increasing attention; however, current solid acids face challenges such as high catalyst loading (low catalytic activity), poor catalyst-substrate interaction, deficient hydrothermal stability, and unsatisfactory recyclability. This review critically discussed the recent efforts and progress in overcoming the issues of solid acids and developing high-performance solid acids for hydrolyzing cellulose. The key structural features of solid acids and their effects on the interactions with cellulose and cellulose hydrolysis were addressed in detail. Strategies and perspectives to enhance performance, hydrothermal stability and recyclability of solid acids were provided. [ABSTRACT FROM AUTHOR]

In order to enhance the enzymatic hydrolysis of lignocelluloses and recycle surfactants after enzymatic hydrolysis, a pH-responsive lignin amphoteric surfactant (SLQA) was prepared by the quaternization of sulfonated lignin (SL). Compared with SL, SLQA could much more effectively enhance the enzymatic hydrolysis of lignocelluloses. With an increase in the quaternization degree, enhancement of the enzymatic hydrolysis of lignocelluloses by the SLQA gradually increased. Adding 2 g L−1 SLQA-80 (mass radio of quaternizing agent to SL was 80%) could increase the enzymatic digestibility of pretreated eucalyptus and corncob residues (CCR) from 36.7% and 37.8% to 84.3% and 90.5%, respectively. The adsorption of SLQA on lignin film was larger than that of SL, and the lignin film became more hydrophilic after adsorbing SLQA. Thus, SLQA could cause more effective steric hindrance and form a hydration layer to reduce the non-productive adsorption of cellulase on lignin. The purified SLQA-80 exhibited sensitive pH-responsive property, and 90.8% of SLQA-80 could be recycled by adjusting the pH of hydrolysate after enzymatic hydrolysis. Adding recyclable SLQA could not only obviously enhance the enzymatic hydrolysis of lignocelluloses, but could also enable the comprehensive utilization of lignocelluloses. This method is of great significance to reducing the cost of cellulosic ethanol. [ABSTRACT FROM AUTHOR]