Gene expression of enzymes involved in utilization of xylooligosaccharides by Lactobacillus strains

Valorization of rice straw and vascular aquatic weeds for sustainable prebiotic hemicellulosic autohydrolysate production: Extraction, characterization and fermentability

This study describes the extraction and characterization of the hemicellulosic autohydrolysates (HAHs) derived from rice straw (RS) and vascular aquatic weeds like Typha angustifolia (TA) and Ceretophyllum demersum (CD). It further explores their capacity to sustain the proliferation of selected lactic acid bacteria (i.e., prebiotic activity) isolated from milk samples. To fractionate HAH from RS, TA and CD hot water extraction (HWE) method was used and RS, TA, and CD biomasses yielded 6.8, 4.99 and 2.98% of HAH corresponding to the hemicellulose extraction efficiencies of 26.15 ± 0.8%, 23.76 ± 0.6%, and 18.62 ± 0.4% respectively. The chemical characterization of HAH concentrates through HPLC showed that they comprised galactose, arabinose, xylose and glucose. The total phenol content of the RS, TA and CD-derived HAH concentrates were 37.53, 56.78 and 48.08 mg GAE/g. The five lactic acid bacteria (LAB) isolates Q1B, Q2A, Q3B, G1C and G2B selected for prebiotic activity assays generated mixed responses with the highest growth in RS-HAH for Q2A and the least in TA-HAH for Q3B. Further, the isolates Q2A, Q3B, G1C, and G2B, which showed the highest growth performance, were identified through MALDI-TOF and 16S rRNA sequencing as Lactobacillus brevis. All the tested LAB isolates showed diauxic growth in crude HAH preparations to maximize the utilization of carbon resources for their proliferation. This suggests that the selected LAB isolates are efficient degraders of hemicellulosic sugars. This paves the way for the valorization of lignocellulosic biomass to produce prebiotic hemicellulosic autohydrolysate and consequently enhances environmental sustainability by improving resource efficiency.

Properties and biotechnological applications of microbial deacetylase

Deacetylases, a class of enzymes that can catalyze the hydrolysis of acetylated substrates to remove the acetyl group, used in producing various products with high qualities, are one of the most influential industrial enzymes. These enzymes are highly specific, non-toxic, sustainable, and eco-friendly biocatalysts. Deacetylases and deacetylated compounds have been widely applicated in pharmaceuticals, medicine, food, and the environment. This review synthetically summarizes deacetylases' sources, characterizations, classifications, and applications. Moreover, the typical structural characteristics of deacetylases from different microbial sources are summarized. We also reviewed the deacetylase-catalyzed reactions for producing various deacetylated compounds, such as chitosan-oligosaccharide (COS), mycothiol, 7-aminocephalosporanic acid (7-ACA), glucosamines, amino acids, and polyamines. It is aimed to expound on the advantages and challenges of deacetylases in industrial applications. Moreover, it also serves perspectives on obtaining promising and innovative biocatalysts for enzymatic deacetylation. KEYPOINTS: • The fundamental properties of microbial deacetylases of various microorganisms are presented. • The biochemical characterizations, structures, and catalyzation mechanisms of microbial deacetylases are summarized. • The applications of microbial deacetylases in food, pharmaceutical, medicine, and the environment were discussed.

Recent Research and Application Prospect of Functional Oligosaccharides on Intestinal Disease Treatment

The intestinal tract is an essential digestive organ of the human body, and damage to the intestinal barrier will lead to various diseases. Functional oligosaccharides are carbohydrates with a low degree of polymerization and exhibit beneficial effects on human intestinal health. Laboratory experiments and clinical studies indicate that functional oligosaccharides repair the damaged intestinal tract and maintain intestinal homeostasis by regulating intestinal barrier function, immune response, and intestinal microbial composition. Functional oligosaccharides treat intestinal disease such as inflammatory bowel disease (IBD) and colorectal cancer (CRC) and have excellent prospects for therapeutic application. Here, we present an overview of the recent research into the effects of functional oligosaccharides on intestinal health.

Preventing Colorectal Cancer through Prebiotics

Colorectal cancer (CRC), the third most common cancer in the world, has been recently rising in emerging countries due to environmental and lifestyle factors. Many of these factors are brought up by industrialization, which includes lack of physical activity, poor diet, circadian rhythm disruption, and increase in alcohol consumption. They can increase the risk of CRC by changing the colonic environment and by altering gut microbiota composition, a state referred to as gut dysbiosis. Prebiotics, which are nutrients that can help maintain intestinal microbial homeostasis and mitigate dysbiosis, could be beneficial in preventing inflammation and CRC. These nutrients can hinder the effects of dysbiosis by encouraging the growth of beneficial bacteria involved in short-chain fatty acids (SCFA) production, anti-inflammatory immunity, maintenance of the intestinal epithelial barrier, pro-apoptotic mechanisms, and other cellular mechanisms. This review aims to summarize recent reports about the implication of prebiotics, and probable mechanisms, in the prevention and treatment of CRC. Various experimental studies, specifically in gut microbiome, have effectively demonstrated the protective effect of prebiotics in the progress of CRC. Hence, comprehensive knowledge is urgent to understand the clinical applications of prebiotics in the prevention or treatment of CRC.

Metabolic Profiling of Xylooligosaccharides by Lactobacilli

Three lactic acid bacteria (LAB) strains identified as Lactobacillus plantarum, Lactobacillus brevis, and Lactobacillus sakei isolated from meat products were tested for their ability to utilize and grow on xylooligosaccharides (XOSs). The extent of carbohydrate utilization by the studied strains was analyzed by HPLC. All three strains showed preferences for the degree of polymerization (DP). The added oligosaccharides induced the LAB to form end-products of typical mixed-acid fermentation. The utilization of XOSs by the microorganisms requires the action of three important enzymes: β-xylosidase (EC 3.2.1.37) exo-oligoxylanase (EC 3.2.1.156) and α-L-arabinofuranosidase (EC 3.2.1.55). The presence of intracellular β-D-xylosidase in Lb. brevis, Lb. plantarum, and Lb. sakei suggest that XOSs might be the first imported into the cell by oligosaccharide transporters, followed by their degradation to xylose. The studies on the influence of XOS intake on the lipids of rat liver plasma membranes showed that oligosaccharides display various beneficial effects for the host organism, which are probably specific for each type of prebiotic used. The utilization of different types of oligosaccharides may help to explain the ability of Lactobacillus strains to compete with other bacteria in the ecosystem of the human gastrointestinal tract.

Novel Synergistic Mechanism for Lignocellulose Degradation by a Thermophilic Filamentous Fungus and a Thermophilic Actinobacterium Based on Functional Proteomics

Effective artificial microbial consortia containing microorganisms with desired biological functions have the potential to optimize the lignocellulose-based bioindustry. Thermobifida fusca was a dominant actinobacterium in high-temperature corn stalk composts, but it was unable to grow alone in corn stalk solid medium. Interestingly, T. fusca showed good growth and secreted enzymes when cocultured with Thermomyces lanuginosus. T. lanuginosus grew firstly during the initial stage, whereas T. fusca dominated the system subsequently during cocultivation. The secretome indicated that T. lanuginosus mainly degraded xylan by expressing a GH11 xylanase (g4601.t1, GenBank AAB94633.1; with relative secretion of 4.95 ± 0.65%). T. fusca was induced by xylan mainly to secrete a xylanase from GH11 family (W8GGR4, GenBank AHK22788.1; with relative secretion of 8.71 ± 3.83%) which could rapidly degrade xylan to xylo-oligosaccharide (XOS) and xylose within 2 min, while high concentrations (>0.5%, w/v) of XOS or xylose suppressed the growth of T. fusca; which may be the reason why T. fusca unable to grow alone in corn stalk solid medium. However, T. lanuginosus could utilize the XOS and xylose produced by xylanases secreted by T. fusca. During the synergistic degradation of lignocellulose by T. lanuginosus and T. fusca, xylan was rapidly consumed by T. lanuginosus, the residual cellulose could specifically induced T. fusca to express a GH10 xylanase with a CBM2 domain (Q47KR6, GenBank AAZ56956.1; with relative secretion of 5.03 ± 1.33%) and 6 cellulases (2 exocellulases and 4 endocellulases). Moreover, T. lanuginosus increased the secretion of cellulases from T. fusca by 19-25%. The order of T. lanuginosus and T. fusca was consistent with the multilayered structures of lignocellulose and could be regulated by different concentrations of XOS and xylose. The novel synergism of T. lanuginosus and T. fusca gave a new sight for revealing more synergetic relationships in natural environments and exploring efficient microbial inoculants and enzyme cocktails for lignocellulose degradation.

Functional Expression and Characterization of Acetyl Xylan Esterases CE Family 7 from Lactobacillus antri and Bacillus halodurans

Acetyl xylan esterase (AXE; E.C. 3.1.1.72) is one of the accessory enzymes for xylan degradation, which can remove the terminal acetate residues from xylan polymers. In this study, two genes encoding putative AXEs (LaAXE and BhAXE) were cloned from Lactobacillus antri DSM 16041 and Bacillus halodurans C-125, and constitutively expressed in Escherichia coli. They possess considerable activities towards various substrates such as p-nitrophenyl acetate, 4-methylumbelliferyl acetate, glucose pentaacetate, and 7-amino cephalosporanic acid. LaAXE and BhAXE showed the highest activities at pH 7.0 and 8.0 at 50°C, respectively. These enzymes are AXE members of carbohydrate esterase (CE) family 7 with the cephalosporine-C deacetylase activity for the production of antibiotics precursors. The simultaneous treatment of LaAXE with Thermotoga neapolitana β-xylanase showed 1.44-fold higher synergistic degradation of beechwood xylan than the single treatment of xylanase, whereas BhAXE showed no significant synergism. It was suggested that LaAXE can deacetylate beechwood xylan and enhance the successive accessibility of xylanase towards the resulting substrates. The novel LaAXE originated from a lactic acid bacterium will be utilized for the enzymatic production of D-xylose and xylooligosaccharides.

Combining of transcriptome and metabolome analyses for understanding the utilization and metabolic pathways of Xylo-oligosaccharide in Bifidobacterium adolescentis ATCC 15703

A combination of transcriptome and metabolome analyses was applied to understand the utilization and metabolism of Xylo-oligosaccharide (XOS) in Bifidobacterium adolescentis 15703 as well as identifying the key regulatory-related genes and metabolites. Samples of cultures grown on either XOS or xylose were collected. The transcript and metabolite profiles were obtained from high-throughput RNA-sequencing data analysis and UHPLC system. Compared with xylose, XOS highly promoted the growth of B. adolescentis 15703 and resulted in a growth yield about 1.5-fold greater than xylose. The transcriptome analysis showed that XOS could enhance genes, including ABC transporters, galactosidase, xylosidase, glucosidase, and amylase, which were involved in transport and metabolism of carbohydrate compared with xylose. Furthermore, the expression profile of 16 candidate genes using qRT-PCR has validated the accuracy of the RNA-seq data. Also, the metabolomic analyses, particularly those related to metabolic biomarkers of fatty acids, amino acids, and sugars showed a similar trend of result and approved the advantages of XOS as growth medium for B. adolescentis 15703 compared with xylose. The expression and abundance of specific genes and metabolites highlighted the complex regulatory mechanisms involved in utilization of XOS by B. adolescentis 15703. These results are useful in the understanding of the metabolic pathway of XOS in B. adolescentis 15703 and contribute to the optimization of XOS probiotic effects as a food additive.

Physiological and molecular insights of bacteriocin production by Enterococcus hirae ST57ACC from Brazilian artisanal cheese

The bacteriocinogenic Enterococcus hirae ST57ACC recently isolated from a Brazilian artisanal cheese was subjected here to additional analyses in order to evaluate its bacteriocin production and the potential influence of ABC transporter system in its expression. Besides these physiological and molecular aspects, the bacteriocin was evaluated for its cytotoxicity against HT-29. Differences in the inoculum size had no impact on the growth of E. hirae ST57ACC; however, the bacteriocin was only produced after 9 h of growth when the strain was inoculated at 5% or 10% (v/v), with similar levels of bacteriocin production obtained by both conventional growth and batch fermentation. Furthermore, potential expression of ABC transporters corresponding to the bacteriocin transport and sugar metabolism was identified. In terms of adverse effects, when a semi-purified fraction of the bacteriocin and the cell-free supernatant were tested against HT-29, total cell viability was similar to observed on untreated cells, indicating the absence of cytotoxic effect. Based on the obtained results, E. hirae ST57ACC can produce its bacteriocin at industrial level by using bioreactors, its bacteriocin expression is potentially influenced by the ABC transporter system, and no cytotoxic effects were observed on HT-29 cells, indicating its potential use as a bio-preservative.

Nutraceuticals in colorectal cancer: A mechanistic approach

Colorectal cancer (CRC) is one of the most diagnosed cancers in the world. Even though screening, surgery and oncology have greatly advanced, CRC is still one of the leading causes of cancer deaths, with 700,000 annual mortalities in both men and women. Environmental and lifestyle factors brought up by industrialization, such as an altered diet, lack of physical activity, increase in alcohol consumption, and circadian disruption, have greatly affected the burden of CRC. These factors increase the CRC risk, at least partly, by pathologically altering the colonic environment, including composition of the gut microbiota, referred to as dysbiosis. Colonic dysbiosis can promote pro-carcinogenic immune signaling cascades, leading to pro-tumorigenic inflammation, carcinogen production, and altered cellular responses in susceptible host resulting to development and/or progression of CRC. Nutraceuticals such as prebiotic molecules and probiotic bacterial species can help maintain intestinal microbial homeostasis and thus mitigate this pathological processes. Therefore, prebiotics and probiotics can hinder the effects of dysbiosis by encouraging anti-carcinogenic, anti-inflammatory immunity, the maintenance of the intestinal epithelial barrier, pro-apoptotic mechanisms, and carcinogen inactivation. In addition to its implications in preventing CRC, because of the mechanisms affected, nutraceuticals are being discovered as potential adjuncts to immune checkpoint inhibitors in the treatment of CRC. In this review, we provide an overview of the potential implications of prebiotics and probiotics in the prevention and treatment of CRC.

Study of prebiotic potential and antioxidant activity in Plantago spp. leaves after enzymatic hydrolysis with hemicellulase and xylanase

The leaves of Plantago species have been known as a rich source of polysaccharides, polyphenols, and iridoids. In the recent years, some authors have examined the relative influence of carbohydrate compositions and polyphenols on their antioxidant and prebiotic activity. In this study enzymatic hydrolysis of Plantago major, Plantago lanceolata, and Plantago media leaves with hemicellulase and xylanase was carried out. The chemical composition of the enzyme-derived hydrolysis products was determined. Their antioxidant activity was evaluated using 2,2-diphenyl-2-picryl-hydrazyl-hydrate, ferric reducing antioxidant power, and cupric reducing antioxidant capacity assays. The utilization of the carbohydrate complex from the obtained hydrolysates to stimulate the production of certain glycohydrolases from Lactobacillus plantarum probiotic strains was investigated. The HPLC analysis of the hydrolysis products showed the presence of galactose and arabinose in 1:3 and 1:4 ratios. The highest concentration of total sugars was determined in P. major hydrolysates with hemicellulase (386.71 mg/g dry weight). The antioxidant activity according to the three methods was the highest in P. media hydrolysates, which correlated with their total phenolic concentration. L. plantarum S27 showed the highest values of α-galactosidase activity at the 24-h fermentation process when it was cultivated in a broth with the presence of P. major hydrolysates with hemicellulase and xylanase (0.129 U/mg and 0.133 U/mg, respectively).

Synthesis of glucooligosaccharides with prebiotic potential by glucansucrase URE 13-300 acceptor reactions with maltose, raffinose and lactose

In the present work, we report an efficient synthesis of glucooligosaccharides (GOSs) with prebiotic potential by novel glucansucrase URE 13-300 from Leuconostoc mesenteroides URE 13 strain. The highest total yield of GOSs with degree of polymerization (DP) from 3 to 6 was obtained with maltose as an acceptor and maltose/sucrose (M/S) ratio 1-136 g/L. An efficient modulation of GOSs composition is achieved by varying the M/S ratio. At M/S = 1, 2, 4 and 7 the content of DP3 products gradually increase from 54.50 to 91.70%. When the M/S ratio was decreased the synthesis of DP>3 GOSs is predominant and reaches 75.60% (M/S = 0.25). In addition, the maltose derived GOSs with DP>3, as well as raffinose and lactose glucosylation products have a branched structure which is prerequisite for increased prebiotic potential. The synthesized GOSs were efficiently metabolized by probiotic strains of Lb. plantarum S26, Lb. brevis S27 and Lb. sakei S16, and the calculated values of specific growth rate (μ) were nearly identical to this on glucose media, when maltose derived GOSs were used as a carbohydrate source. Strain specific features were observed in the utilization of the synthesized GOSs, as well as in the production of lactic acid and acetic acid.

Transcriptomic Analysis of Xylan Oligosaccharide Utilization Systems in Pediococcus acidilactici Strain BCC-1

Xylan oligosaccharides (XOS) are the hydrolysates of xylan. To compare the proliferation effect of XOS, glucose, fructo oligosaccharides (FOS), xylose, XOS, and a media without carbohydrate source (control) on Pediococcus acidilactici strain BCC-1, the de novo sequencing of Pediococcus acidilactici strain BCC-1 was conducted, and the underlying mechanism of prebiotic xylo oligosaccharide between xylose and XOS was revealed through transcriptomic analysis. Compared to FOS, glucose, and xylose, XOS exhibits a good performance in promoting the fermentation of Pediococcus acidilactici BCC-1. The genome of Pediococcus acidilactici BCC-1 revealed genes encoding XOS transportation and utilized related enzymes, including ATP-binding cassette (ABC) transporters, arabinofuranosidase, xylanase, xylosidase, xylose isomerase, and xylulose kinase. Transcriptome analysis showed that XOS treatment enhanced genes involving carbohydrate metabolism, an ABC transporter sugar system, pentose and glucuronate interconversions, pyruvate metabolism, and the TCA process when compared to xylose treatment. It suggested XOS treatment enhanced sugar absorption and utilization. These results are useful in the understanding of the metabolic pathway of XOS in Pediococcus acidilactici BBC-1 and may contribute to the optimization of the probiotic effect of Pediococcus acidilactici BCC-1 as novel complex feed additives.

Extrusion of barley and oat influence the fecal microbiota and SCFA profile of growing pigs

The effect of extrusion of barley and oat on the fecal microbiota and the formation of SCFA was evaluated using growing pigs as model system. The pigs were fed a diet containing either whole grain barley (BU), oat groat (OU), or their respective extruded samples (BE and OE).