Bioprocess development for the production of xylooligosaccharide prebiotics from agro-industrial lignocellulosic waste

A novel GH11 β-1,4-xylanase from Fusarium verticillioides: Its eukaryotic expression, biochemical characterization and synergistic effect with cellulase on lignocellulosic biomass degradation

A recently discovered GH11 β-xylanase, FvXynA, from the phytopathogenic fungus Fusarium verticillioides was overexpressed in Pichia pastoris and displayed the highest activity toward beechwood xylan (1258.7 IU/mg) under the optimum reaction conditions of 50 °C and pH 5.0. FvXynA exhibited remarkable thermo-acid/alkali stability and showed good tolerance to various chemical reagents. The presence of 10 mM Ca2+ and Ni2 significantly stimulated, whereas that of Zn2+, Mn2+, Co2+ and Fe3+ negatively affected, FvXynA activity. TLC analysis demonstrated that FvXynA promoted the continuous saccharification of xylan into xylooligosaccharides, mainly xylobiose to xylopentose. Furthermore, FvXynA exerted a marked synergistic effect with the commercial cellulase in the degradation of sodium hydroxide-pretreated agricultural biomass materials, including corn stover, rice straw and wheat straw. Additionally, many valuable oligosaccharides were generated by the effective saccharification of these pretreated biomasses with this enzymatic cocktail. This discovery paves the way for identifying usable xylanases derived from plant pathogenic fungi and suggests a promising biocatalyst for biomass conversion in industrial practices.

Bioprocessing of pineapple leaf waste biomass using an integrated ultrasound-deep eutectic solvent pretreatment approach for improved bioethanol production

Biorefineries play a crucial role in advancing the circular bioeconomy by integrating the environmental and socio-economic dimensions of the industrial sector. This study investigated the potential of integrated ultrasound (UL)-deep eutectic solvent (DES, choline chloride/glycerol) pretreatment of pineapple leaf (PL) waste for efficient bioethanol production, emphasizing its sustainability and environmental benefits. The pretreatment conditions were optimized using response surface methodology, with variables including ultrasound amplitude (45%), time (30min), and solid loading (10%, w/w). The solid PL biomass was physico-chemically characterized, revealing prominent variations in functional groups, surface morphology, crystallinity, and surface area across samples subjected to individual and integrated pretreatment approaches. A high reducing sugar yield of 324.41mg/g PL biomass was recovered after enzymatic hydrolysis of integrated UL-ChCl/glycerol pretreated PL samples under optimized conditions. The fermentation of the sugar hydrolysate yielded a 121.36mg/g ethanol with 89.61% fermentation efficiency. Notably, DES recyclability experiments indicated significant performance up to the third cycle, after which activity marginally declined in correlation with sugar yield. The synergistic UL-ChCl/glycerol pretreatment process supports circular bioeconomy by promoting sustainable biomass conversion and offering a promising approach to reducing environmental impacts by utilizing agricultural waste for renewable energy production.

Xylooligosaccharide recovery from sugarcane bagasse using β-xylosidase-less xylanase, BsXln1, produced by Bacillus stercoris DWS1: Characterization, antioxidant potential and influence on probiotics growth under anaerobic conditions

Xylooligosaccharides (XOS) are excellent prebiotic which improve health through selective modulation of beneficial gut microbiome. Its production from agroresidues using microbial xylanase is considered as sustainable and economic approach. In this study a xylanase producing bacterium isolated from decaying wood soil was phylogenetically identified and designated as Bacillus stercoris DWS1. Xylanase (BsXln1) purified from the bacterium had pH and temperature optima of 7 and 37-60 °C, respectively, and it retained 85 % activity upon preincubation at 60 °C for 40 min. Indicating its moderate thermostability. Zymogram analysis of partially purified BsXln1 revealed its molecular weight of ~35 kDa. B. stercoris DWS1 produced 200 U mL-1 of BsXln1 in presence of 1.5 % sugarcane bagasse (SCB) as carbon source; which was enhanced to 591 U mL-1 through optimization of cultural conditions. Xylan extracted from SCB was morphologically and structurally characterized, and then depolymerized by BsXln1 to yield XOS (400 mg g-1). Analysis of purified XOS by TLC, followed by ESI-MS showed predominance of xylobiose and xylotriose. XOS exhibited in vitro antioxidant activities against DPPH and ABTS free radicals, however, it had limited prebiotic activity on Lactobacillus plantarum and Lactobacillus fermentum under anaerobic condition. In conclusion, the xylanase, BsXln1, produced by B. stercoris DWS1 can be used in food industries for efficient production of bioactive XOS from agroresidues.

Food Waste Biotransformation into Food Ingredients: A Brief Overview of Challenges and Opportunities

In today's global context, challenges persist in preventing agri-food waste due to factors like limited consumer awareness and improper food-handling practices throughout the entire farm-to-fork continuum. Introducing a forward-thinking solution, the upcycling of renewable feedstock materials (i.e., agri-food waste and by-products) into value-added ingredients presents an opportunity for a more sustainable and circular food value chain. While multi-product cascade biorefining schemes show promise due to their greater techno-economic viability, several biotechnological hurdles remain to be overcome at many levels. This mini-review provides a succinct overview of the biotechnological and societal challenges requiring attention while highlighting valuable food-grade compounds derived from biotransformation processes. These bio-based ingredients include organic acids, phenolic compounds, bioactive peptides, and sugars and offer diverse applications as antioxidants, preservatives, flavorings, sweeteners, or prebiotics in foodstuffs and other consumer goods. Therefore, these upcycled products emerge as a sustainable alternative to certain potentially harmful artificial food additives that are still in use or have already been banned from the industry.

Halosquirtibacter laminarini gen. nov., sp. nov. and Halosquirtibacter xylanolyticus sp. nov., marine anaerobic laminarin and xylan degraders in the phylum Bacteroidota

The bacterial group of the phylum Bacteroidota greatly contributes to the global carbon cycle in marine ecosystems through its specialized ability to degrade marine polysaccharides. In this study, it is proposed that two novel facultative anaerobic strains, DS1-an-13321T and DS1-an-2312T, which were isolated from a sea squirt, represent a novel genus, Halosquirtibacter, with two novel species in the family Prolixibacteraceae. The 16S rRNA sequence similarities of these two strains were 91.26% and 91.37%, respectively, against Puteibacter caeruleilacunae JC036T, which is the closest recognized neighbor. The complete genomes of strains DS1-an-13321T and DS1-an-2312T each consisted of a single circular chromosome with a size of 4.47 and 5.19 Mb, respectively. The average amino acid identity and the percentage of conserved proteins against the type species of the genera in the family Prolixibacteraceae ranged from 48.33 to 52.35% and 28.34-37.37%, respectively, which are lower than the threshold for genus demarcation. Strains DS1-an-13321T and DS1-an-2312T could grow on galactose, glucose, maltose, lactose, sucrose, laminarin, and starch, and only DS1-an-2312T could grow on xylose and xylan under fermentation conditions. These strains produced acetic acid and propionic acid as the major fermentation products. Genome mining of the genomes of the two strains revealed 27 and 34 polysaccharide utilization loci, which included 155 and 249 carbohydrate-active enzymes (CAZymes), covering 57 and 65 CAZymes families, respectively. The laminarin-degrading enzymes in both strains were cell-associated, and showed exo-hydrolytic activity releasing glucose as a major product. The xylan-degrading enzymes of strain DS1-an-2312T was also cell-associated, and had endo-hydrolytic activities, releasing xylotriose and xylotetraose as major products. The evidence from phenotypic, biochemical, chemotaxonomic, and genomic characteristics supported the proposal of a novel genus with two novel species in the family Prolixibacteraceae, for which the names Halosquirtibacter laminarini gen. nov., sp. nov. and Halosquirtibacter xylanolyticus sp. nov. are proposed. The type strain of Halosquirtibacter laminarini is DS1-an-13321T (= KCTC 25031T = DSM 115329T) and the type strain of Halosquirtibacter xylanolyticus is DS1-an-2312T (= KCTC 25032T = DSM 115328T).

Effect of Bioactive Peptides on Gut Microbiota and Their Relations to Human Health

Bioactive peptides derived from both exogenous and endogenous origins have been studied extensively to use their beneficial effects in humans and animals. Bioactive peptides exhibit beneficial bodily functions and contribute to a healthy gastrointestinal system by influencing barrier functions, immune responses, and gut microbiota. Gut microbiota is a diverse microbial community that significantly influences the overall well-being and homeostasis of the body. Factors such as diet, age, lifestyle, medication, and environmental circumstances can affect the composition and diversity of the gut microbiota. The disturbances or imbalances in the gut microbiota have been associated with various health problems. The interplays between bioactive peptides and gut microbiota are not fully understood, but bioactive peptides hold promise as modulators of the gut microbiota to promote gut health. Almost all the bioactive research on human health, including the development of therapeutics and nutritional interventions, uses cell culture, even though their direct biofunctional activities can only occur when absorbed in the intestine and into the blood system. This review focuses on the current understanding of bioactive peptides in gut microbiota and their impact and mechanisms on gut and human health. The novelty of this review lies in its comprehensive analysis of the multifaceted interactions between bioactive peptides and gut microbiota, integrating knowledge from diverse disciplines between microbiology and nutrition. By elucidating the underlying mechanisms and identifying current research gaps, this review offers an outlook on the potential of bioactive peptides in promoting gut health and shaping future therapeutic and nutritional interventions.

Synergistic microwave and acidic deep eutectic solvent-based pretreatment of Theobroma cacao pod husk biomass for xylooligosaccharides production

The bioconversion of lignocellulosic biomass into novel bioproducts is crucial for sustainable biorefineries, providing an integrated solution for circular economy objectives. The current study investigated a novel microwave-assisted acidic deep eutectic solvent (DES) pretreatment of waste cocoa pod husk (CPH) biomass to extract xylooligosaccharides (XOS). The sequential DES (choline chloride/citric acid, molar ratio 1:1) and microwave (450W) pretreatment of CPH biomass was effective in 67.3% xylan removal with a 52% XOS yield from total xylan. Among different XOS of varying degrees of polymerization, a higher xylobiose content corresponding to 69.3% of the total XOS (68.22 mg/g CPH) from liquid fraction was observed. Enzymatic hydrolysis of residual xylan from pretreated CPH biomass with low commercial xylanase (10 IU/g) concentration yielded 24.2% XOS. The MW-ChCl/citric acid synergistic pretreatment approach holds great promise for developing a cost-effective and environmentally friendly method contributing to the sustainable production of XOS from agricultural waste streams.

Computation-Aided Phylogeny-Oriented Engineering of β-Xylosidase: Modification of "Blades" to Enhance Stability and Activity for the Bioconversion of Hemicellulose to Produce Xylose

Hemicellulose is a highly abundant, ubiquitous, and renewable natural polysaccharide, widely present in agricultural and forestry residues. The enzymatic hydrolysis of hemicellulose has generally been accomplished using β-xylosidases, but concomitantly increasing the stability and activity of these enzymes remains challenging. Here, we rationally engineered a β-xylosidase from Bacillus clausii to enhance its stability by computation-aided design combining ancestral sequence reconstruction and structural analysis. The resulting combinatorial mutant rXYLOM25I/S51L/S79E exhibited highly improved robustness, with a 6.9-fold increase of the half-life at 60 °C, while also exhibiting improved pH stability, catalytic efficiency, and hydrolytic activity. Structural analysis demonstrated that additional interactions among the propeller blades in the catalytic module resulted in a much more compact protein structure and induced the rearrangement of the opposing catalytic pocket to mediate the observed improvement of activity. Our work provides a robust biocatalyst for the hydrolysis of agricultural waste to produce various high-value-added chemicals and biofuels.

Optimization of Xylooligosaccharides Production by Native and Recombinant Xylanase Hydrolysis of Chicken Feed Substrates

Poultry production faces several challenges, with feed efficiency being the main factor that can be influenced through the use of different nutritional strategies. Xylooligosaccharides (XOS) are functional feed additives that are attracting growing commercial interest due to their excellent ability to modulate the composition of the gut microbiota. The aim of the study was to apply crude and purified fungal xylanases, from Trichoderma harzianum, as well as a recombinant glycoside hydrolase family 10 xylanase, derived from Geobacillus stearothermophilus T6, as additives to locally produced chicken feeds. A Box-Behnken Design (BBD) was used to optimize the reducing sugar yield. Response surface methodology (RSM) revealed that reducing sugars were higher (8.05 mg/mL, 2.81 mg/mL and 2.98 mg/mL) for the starter feed treated with each of the three enzymes compared to the treatment with grower feed (3.11 mg/mL, 2.41 mg/mL and 2.62 mg/mL). The hydrolysis products were analysed by thin-layer chromatography (TLC), and high-performance liquid chromatography (HPLC) analysis and showed that the enzymes hydrolysed the chicken feeds, producing a range of monosaccharides (arabinose, mannose, glucose, and galactose) and XOS, with xylobiose being the predominant XOS. These results show promising data for future applications as additives to poultry feeds.

Insights into the recent advances of agro-industrial waste valorization for sustainable biogas production

Recent years have seen a transition to a sustainable circular economy model that uses agro-industrial waste biomass waste to produce energy while reducing trash and greenhouse gas emissions. Biogas production from lignocellulosic biomass (LCB) is an alternative option in the hunt for clean and renewable fuels. Different approaches are employed to transform the LCB to biogas, including pretreatment, anaerobic digestion (AD), and biogas upgradation to biomethane. To maintain process stability and improve AD performance, machine learning (ML) tools are being applied in real-time monitoring, predicting, and optimizing the biogas production process. An environmental life cycle assessment approach for biogas production systems is essential to calculate greenhouse gas emissions. The current review presents a detailed overview of the utilization of agro-waste for sustainable biogas production. Different methods of waste biomass processing and valorization are discussed that contribute towards developing an efficient agro-waste to biogas-based circular economy.