Viticulture in hyper-arid environments represents an emerging frontier in non-traditional winegrowing regions, where extreme climatic conditions may be associated with distinctive grape and wine chemical composition. In this study, four wines produced from Vitis vinifera cv. Tamarugal cultivated in the Atacama Desert (Chile) were characterized based on their volatile organic compound composition, with particular emphasis on free and glycosylated aroma-related volatile fractions. Wines from four production years (2019–2022), obtained under different vinification approaches, were analyzed using solid-phase extraction followed by GC–MS. The free volatile fraction was dominated by lipid-derived compounds, including fatty acid-derived alcohols, acids, and esters, whereas the glycosylated fraction was enriched in C13-norisoprenoids and benzenoid/phenylpropanoid-derived precursors, highlighting a substantial pool of bound volatile compounds. Multivariate analyses, including principal component analysis (PCA) and supervised partial least squares–discriminant analysis (PLS-DA), were applied to explore patterns in volatile composition and support visualization of variables associated with sample differentiation. The observed compositional differences were associated with the combined influence of vintage and vinification conditions, which could not be experimentally disentangled in the present study. This study provides the first characterization of free and glycosylated volatile profiles in wines produced in the Atacama Desert and contributes to the understanding of wines from non-traditional hyper-arid viticultural conditions.
Olive industry by-products, particularly olive pomace (OLP), extracted olive pomace (EOLP), and olive stones (OLS), are promising alternative substrates for oligosaccharide (OS) production, as their polysaccharides can be converted into OS by physicochemical treatment, enzymatic hydrolysis, or direct fermentation. However, OS mixtures and one-step strategies integrating enzyme production and substrate conversion remain underexplored. This review evaluates OLP, EOLP, and OLS as raw materials for producing XOS-rich and POS-related oligosaccharides, as well as OS mixtures with prebiotic and technological potential, emphasising direct fermentation. A structured literature mapping was used to compare substrate types, product classes, and production strategies. Conventional physicochemical and enzymatic strategies are compared with the emerging direct fermentation strategy in terms of substrate accessibility, OS yield, degree of polymerisation, product composition, downstream requirements. Physicochemical processes enable rapid solubilisation but require careful control to limit over-depolymerisation, whereas enzymatic hydrolysis provides greater selectivity but depends on substrate accessibility and enzyme inputs. Direct fermentation integrates enzyme production and substrate conversion, although product control and recovery remain challenging. Human evidence is strongest for XOS, while POS and OS mixtures require direct validation. Further progress requires linking substrate composition and process selection to product standardisation, biological validation, and application-oriented testing.
The use of cottonseed hulls as a feed resource is constrained by their high fiber content and residual free gossypol. This study evaluated the effects of steam explosion combined with fermentation using a microbial–enzyme preparation on the nutrient composition, fermentation quality, bacterial communities, and in vitro digestion and fermentation characteristics of cottonseed hulls. Four treatments were evaluated using physicochemical analyses, 16S rRNA gene sequencing, and in vitro incubation: an untreated control (CK), steam explosion (BP), fermentation with a microbial–enzyme preparation (FJ), and steam explosion followed by fermentation with the same preparation (BF). All processing treatments significantly reduced free gossypol content (p < 0.05), with BF showing the lowest concentration (70.42 mg/kg), representing a 77.89% reduction relative to CK. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of BF were 573.38 and 446.23 g/kg dry matter (DM), respectively, both significantly lower than those of CK (p < 0.05) but not significantly different from those of BP. Crude protein content did not differ significantly among treatments. BF had the highest lactic acid content (27.94 g/kg DM) and the lowest endpoint pH (4.12). Bacterial community analysis showed that Firmicutes was the dominant phylum in all three fermented groups. At the end of fermentation, Lentilactobacillus was the dominant genus in the BF group, with a relative abundance of 97.55%. No associations between bacterial taxa and fermentation parameters remained significant after correction for multiple testing. KEGG functional prediction indicated differences in potential functional composition among treatments. In vitro DM digestibility in BF reached 43.99% at 48 h; however, NDF digestibility did not differ significantly among treatments at any incubation time. Cumulative gas production and total volatile fatty acid concentration in BF at 48 h were 154.28 mL/g DM and 64.58 mmol/L, respectively, neither of which differed significantly from FJ. In conclusion, steam explosion combined with microbial–enzyme fermentation reduced free gossypol content, promoted lactic acid accumulation, and altered bacterial community composition, providing experimental evidence to support further development of cottonseed hulls as a feed resource.
Spontaneous fermentations contribute to the identity of ancestral mezcal, although duration and yield may vary. This study selected an indigenous yeast and evaluated it as a starter candidate. Four native isolates (Torulaspora delbrueckii A1GM and A6GM, Kluyveromyces marxianus A2GM, and Saccharomyces cerevisiae A5GM) and a spontaneous control were compared in Agave cupreata microfermentations. Selection considered distillate alcohol content and preliminary ethanol-tolerance assays. A5GM was subsequently evaluated in three production batches containing A. angustifolia + A. karwinskii, A. angustifolia, or A. cupreata + A. angustifolia, with three independent vats per treatment. Fermentation profiles, distillate composition, yield, and sensory acceptance were assessed. A5GM produced the highest microfermentation distillate alcohol content (43.91 ± 0.89% Alc. Vol.) and grew at 16% ethanol (v/v). In the first two production batches, inoculated vats showed higher volumes standardized to 45% Alc. Vol. and lower calculated agave requirements than the controls; these were batch-specific observations under the operating conditions studied. Sensory evaluation used pooled vat-derived distillate composites, and the A5GM composites received the highest mean hedonic scores. Because strain-level establishment and persistence of A5GM were not confirmed, the observed outcomes cannot be attributed exclusively to this strain. Sensory interpretation is limited by fixed presentation order. Further independent batches, standardized management, and strain-level monitoring are needed to assess reproducibility.
Increasing the solids concentration in farm dairy effluent is necessary to operate a biogas plant at optimal parameters; however, conventional chemicals reduce CH4 production. This study evaluated the effects of the tannin-based coagulant–flocculant Tanfloc SG® on anaerobic digester performance using biomethane potential (BMP) tests with centrifuged solids produced at 50–300 mg Tanfloc g TS−1, and semi-continuous fermentation tests with settled solids at 150 mg g TS−1 (Tanfloc150). In the fermentation tests, the control and Tanfloc-treated solids were fed into two reactors, operating at 37 °C, at 2.1 kg VS m−3 d−1 with a 12- to 15-day hydraulic retention time. In the BMP tests, the Tanfloc-treated solids showed delayed degradation and produced 168.2–303.1 L CH4 kg VS−1, values not significantly different from the untreated solids (250.0 L CH4 kg VS−1). However, semi-continuous feeding reduced the volatile solids degradation, biogas, and specific CH4 yield by 23.3%, 17.9%, and 24.1%, while the pH, volatile fatty acids, and ammonia-N remained stable. However, Tanfloc150 reduced the biogas H2S and NH3 concentrations and increased the digestate N and S. The lower performance was associated with lower substrate biodegradability, which was consistent with the delayed degradation observed in the BMP tests. These findings highlight the importance of assessing coagulated solids under conditions representative of long-term performance.
