Search

Abstract: In the present study, two granular systems were compared in terms of hydrogen production rate, stability and bacterial diversity under extreme thermophilic conditions (70°C). Two EGSB reactors were individually inoculated with heat treated methanogenic granules (HTG) and HTG amended with enrichment culture with high capacity of hydrogen production (engineered heat treated methanogenic granules – EHTG), respectively. The reactor inoculated with EHTG (R EHTG) attained a maximum production rate of 2.7l H2 l−1day−1 in steady state. In comparison, the R HTG containing the HTG granules was very unstable, with low hydrogen productions and only two peaks of hydrogen (0.8 and 1.5l H2 l−1day−1). The presence of active hydrogen producers in the R EHTG system during the reactor start-up resulted in the development of an efficient H2-producing bacterial community. The results showed that “engineered inocula” where known hydrogen producers are co-inoculated with HTG is an efficient way to start up biohydrogen-producing reactors. [ABSTRACT FROM AUTHOR]

Innovation of pastry products towards higher nutritional and commercial value remains a challenge to the growing field of healthy food. In this study, the prebiotic supplementation and sugar reduction were explored in a widely consumed pastry product with a low level of innovation. The prebiotic potential of commercial agave inulin and galacto-oligosaccharides (GOS) was evaluated and compared by an in vitro model using human fecal inocula. Rice muffins containing 100% of sugar or 75% of sugar supplemented with 0.8% GOS were produced and compared with commercial rice muffins regarding their physical and textural properties. GOS fermentation led to the highest production of lactate and short-chain fatty acids, besides the most significant reduction of the final pH value and of the ammonia and methane production. Inulin presented a higher selectivity towards Lactobacillaceae (51 ± 1% of all), while GOS are more efficient to stimulate Bifidobacteriaceae growth (65 ± 7% of all). Both prebiotics were effective in reducing Methanobacteria. The reduction of sugar content modified the air bubbles characteristics (size and population with a greater number of tunnels) present in the muffin crumb, without relevant differences in apparent porosity. Textural results indicated that springiness and resilience of the muffin with low sugar content are acceptable, but hardness and chewiness were increased. The new-formula muffins presented very relevant textural parameters with comparable values to those reported in the literature for the commercial ones, thus anticipating a good consumer acceptance. This study is an important contribution towards more innovative and diversified healthy pastry products. [Display omitted] • The in vitro fermentation of inulin and GOS was evaluated using human fecal inocula. • GOS led to the highest bifidogenic effect and production of SCFA and gases. • Both prebiotics were effective in reducing Methanobacteria and Proteobacteria. • Rice muffins formulated with GOS and sugar reduction were produced. • Sugar reduction did not alter significantly springiness and resilience of the cakes. [ABSTRACT FROM AUTHOR]

Microbial conversion of carbon monoxide (CO)/syngas has been extensively investigated. The microbial conversion of CO/syngas offers numerous advantages over chemically catalyzed processes e.g. the specificity of the biocatalysts, the operation at ambient conditions and high conversion efficiencies. Bioelectrochemical systems (BESs) exploit the capacity of electrochemically active bacteria (EAB) to use insoluble electron acceptors or donors to produce electricity or added-value compounds. Electricity production from different organic sources in BESs has been broadly demonstrated, whereas electricity production from CO/syngas has been very little reported. Acetate oxidation by a consortium of carboxydotrophic and CO-tolerant EAB has been suggested to be the main pathway responsible for indirect electricity generation from CO/syngas. Although electricity production in BESs from several organic sources has been widely investigated, the interest on BESs research is currently moving to the production of added-value compounds by electro-fermentation (EF) processes. EF allows to modify redox balances by the use of electric circuits to fine tune metabolic pathways towards obtaining products with high economic value. Although EF has been widely studied, the potential of use CO-rich gas streams as substrate has been under explored. This review presents and discusses current advances on microbial conversion of CO/syngas in BESs. • Bioelectrochemical systems have been proposed for microbial conversion of syngas. • Syngas conversion relies on a consortium of CO-tolerant EAB and carboxydotrophs. • Acetate oxidation seems to be the main pathway for indirect electricity production. • Acetate has been reported as the main product of syngas electro-fermentation. • Syngas electro-fermentation is a promising strategy to obtain compounds of interest. [ABSTRACT FROM AUTHOR]

• Hydrolysates containing XOS were obtained by different enzymatic approaches. • Different approaches resulted in XOS with distinct sizes, linkages, and branches. • The hydrolysates showed distinct TFC and FVC amounts and antioxidant properties. • The fermentation of hydrolysates increased SCFAs and gases production. • The relative abundance of beneficial microbiota increased in presence of hydrolysates. This study explores the structural characterization, antioxidant and prebiotic activities of hydrolysates containing xylooligosaccharides (XOS) produced by different strategies: direct fermentation of beechwood xylan (FermBX) and enzymatic treatment of beechwood (EnzBX) and rice husk (EnzRH) xylans. EnzBX and EnzRH showed XOS with a backbone of (1 → 4)-linked-xylopyranosyl residues and branches of arabinose, galactose, and uronic acids. FermBX presented the highest content of total phenolic compounds (14 mg GAE/g) and flavonoids (0.6 mg QE/g), which may contribute to its antioxidant capacity –39.1 μmol TE/g (DPPH), 45.7 μmol TE/g (ABTS), and 79.9 μmol Fe II/g (FRAP). The fermentation of hydrolysates decreased the abundance of microorganisms associated with intestinal diseases from Eubacteriales , Desulfovibrionales and Methanobacteriales orders, while stimulating the growth of organisms belonging to Bacteroides , Megamonas and Limosilactobacillus genera. The production of short-chain fatty acids, ammonia, and CO 2 suggested the prebiotic potential. In conclusion, hydrolysates without previous purification and obtained from non-chemical approaches demonstrated promising biological activities for further food applications. [ABSTRACT FROM AUTHOR]

• The fermentation of XOS and lactulose increased SCFAs and gases production. • The highest concentration of butyrate and CO2 was obtained for XOS. • Both substrates led to a reduction in the ammonia concentration and final pH. • The relative abundance of Bacteroides increased with the addition of XOS. • XOS present potential functional properties for human health. Xylooligosaccharides (XOS) are emergent prebiotics exhibiting high potential as food ingredients. In this work, in vitro studies were performed using human fecal inocula from two healthy donors (D 1 and D2) to evaluate the prebiotic effect of commercial lactulose and XOS produced in a single-step by recombinant Bacillus subtilis 3610. The fermentation of lactulose led to the highest production of lactate (D1: 33.7 ± 0.5 mM; D2:19.7 ± 0.3 mM) and acetate (D1: 77.5 ± 0.6 mM; D2: 81.0 ± 0.7 mM), while XOS led to the highest production of butyrate (D1: 9.0 ± 0.6 mM; D2: 10.5 ± 0.8 mM) and CO 2 (D1: 8.92 ± 0.02 mM; D2: 11.4 ± 0.3 mM). Microbiota analysis showed a significant decrease in the relative abundance of Proteobacteria for both substrates and an increase in Bifidobacterium and Lactobacillus for lactulose, and Bacteroides for XOS. [ABSTRACT FROM AUTHOR]