Search Results (11)

Background: Our previous study showed that antibiotic exposure was linked to depressive symptomatology in community-dwelling older adults in China. Our current study aims to explore the underlying mechanisms by assessing the intermediated effects of circulating short-chain organic acids (SCOAs) on this association. Methods: Depressive symptoms were screened by the 30-item Geriatric Depression Scale (GDS-30). Urinary concentrations of antibiotics and serum SCOAs were measured using a liquid chromatography–mass spectrometry method. Results: Increased exposure to sulfadiazine, azithromycin, tetracyclines, or veterinary antibiotics (VAs) was positively associated with GDS-30 scores. Tetracycline reduced levels of caproic acid, iso-butyric acid, and iso-caproic acid (iso-CA), with iso-CA concentration inversely correlating with GDS-30 scores, while β-hydroxybutyric acids showed a positive correlation. The mediating effect of serum iso-CA on the association between depression and ofloxacin, with a mediating effect of 25.3%, and the association between depression and tetracycline, with a mediating effect of 46.3%, were both statistically significant, indicating partial mediation. Conclusions: Antibiotics may affect the levels of SCOAs in older adults and could potentially contribute to depressive symptoms by influencing alterations in serum iso-CA levels. Full article

Food industry waste and wastewater have been explored in relation to acidogenic fermentation as sources of non-competing food carbohydrates and mixed microbial cultures (MMCs), respectively, with the aim of producing short-chain organic acids (SCOAs) with general applications in polyhydroxyalkanoates (PHAs) production. However, studies on acidogenic fermentation using lipidic substrates are scarce. In this work, it was hypothesized that spent frying oil (SFO) could be used as a substrate for SCOA production via MMCs. In this study, oleic acid was used as a model molecule. The characterization of SFO revealed that it is mainly composed of oleic acid (81%), with minor amounts of palmitic, linoleic, and stearic acids. Different MMCs and food-to-microorganism (F/M) ratios were tested. MMCs collected in the aerobic tank of a municipal wastewater treatment plant (AES), at a 1:1 F/M, allowed to obtain the highest SCOA concentration (1.50 g COD/L) and the most diverse profile of SCOAs, with the production of acetic, propionic, butyric, iso-butyric, and valeric acids at 48:17:9:13:13% on a molar basis, respectively. This variety of odd and even SCOAs is of upmost importance, with potential applications in producing PHAs. This work can be considered a starting point for future acidogenic fermentation studies using lipid-based substrates and for the future production of PHAs. Full article

Anaerobic fermentation (AF) to produce sustainable short-chain organic acids (SCOAs) has found no commercial application so far. This is due to several limitations, including the high energy consumption of the SCOAs’ separation from water by distillation. This study used AspenPlus simulations to investigate the benefits of reverse osmosis (RO) to remove water and concentrate the SCOAs from AF before their separation by distillation. The effect of RO on distillation reflux ratio, heat energy requirements, column diameter and equipment costs was simulated for the processing of model SCOA-containing streams, representing AF effluents. A total of 90 simulations were carried out, investigating three different SCOA compositions, corresponding to different ratios of lactic, acetic and propionic acids, three different concentrations of the total SCOAs (10, 50, 100 g/kg in the stream entering RO) and different extents of water removal by RO. RO brought a reduction in the distillation reboilers’ duty of up to more than 90%, with a reduction of column diameter of up to more than 70%. The total energy consumption, equipment cost and NPV (net present value) of the RO plus distillation process were in all cases more favourable than for the process without membranes. Full article

Spent coffee grounds (SCGs) are a promising substrate that can be valorized by biotechnological processes, such as for short-chain organic acid (SCOA) production, but their complex structure implies the application of a pretreatment step to increase their biodegradability. Physicochemical pretreatments are widely studied but have multiple drawbacks. An alternative is the application of biological pretreatments that include using fungi Trametes versicolor and Paecilomyces variotii that naturally can degrade complex substrates such as SCGs. This study intended to compare acidic and basic hydrolysis and supercritical CO₂ extraction with the application of these fungi. The highest concentration of SCOAs, 2.52 gCOD/L, was achieved after the acidification of SCGs pretreated with acid hydrolysis, but a very similar result, 2.44 gCOD/L, was obtained after submerged fermentation of SCGs by T. versicolor. This pretreatment also resulted in the best acidification degree, 48%, a very promising result compared to the 13% obtained with the control, untreated SCGs, highlighting the potential of biological pretreatments. Full article

Acidogenic fermentation (AF) is often applied to wastes to produce short-chain organic acids (SCOAs)—molecules with applications in many industries. Spent coffee grounds (SCGs) are a residue from the coffee industry that is rich in carbohydrates, having the potential to be valorized by this process. However, given the recalcitrant nature of this waste, the addition of a pretreatment step can significantly improve AF. In this work, several pretreatment strategies were applied to SCGs (acidic hydrolysis, basic hydrolysis, hydrothermal, microwave, ultrasounds, and supercritical CO₂ extraction), evaluated in terms of sugar and inhibitors release, and used in AF. Despite the low yields of sugar extracted, almost all pretreatments increased SCOAs production. Milder extraction conditions also resulted in lower concentrations of inhibitory compounds and, consequently, in a higher concentration of SCOAs. The best results were obtained with acidic hydrolysis of 5%, leading to a production of 1.33 gSCOAs/L, an increase of 185% compared with untreated SCGs. Full article

As an alternative to conventional anaerobic digestion for methane production, anaerobic fermentation (AF) of organic matter can produce short chain organic acids (SCOAs) in a sustainable way. This study investigated the effect of microwave (MW) pre-treatment on the AF of model food waste to SCOAs and ethanol. The MW pre-treatment was investigated at three temperatures (120, 150 and 180 °C) and residence times (2, 5 and 8 min). The MW treatment gave a significant reduction in the pH and volatile suspended solids (VSS). The largest reduction in the VSS was 20%, indicating solubilisation of the organic matter. The latter was also confirmed by the increase, although it was not statistically significant, in the soluble chemical oxygen demand (COD) and soluble carbohydrates. In the fermentation batch tests, the total product yield was higher (17.5% COD COD⁻¹) than for the untreated substrate (11.1% COD COD⁻¹). An electricity price of GBP 0.06 kWh⁻¹ would correspond to the market value of the additional SCOAs produced with the pre-treated substrate. Although this price is lower than the current business price of electricity in the UK, the MW pre-treatment could become economically feasible with scale-up effects and by using free excess electricity coming from renewable resources. Full article

In order to make anaerobic digestion-based processes for short chain organic acid (SCOA) production attractive, the key performance variables, i.e., concentration, yield, and productivity of the produced SCOAs need to be maximised. This study analysed recent literature, looking for the effect of process operating parameters (feed concentration, pH, temperature, and residence time) on the performance variables. Data from 551 experiments were analysed. Mean values of the SCOA concentration, yield, and productivity were 10 g l⁻¹, 32% (chemical oxygen demand (COD) COD⁻¹), and 1.9 g l⁻¹ day⁻¹, respectively. Feed concentration and residence time had the most important effect. Higher feed concentration corresponded to higher product concentration and productivity, but to lower yield. The mean feed concentration was 109 gCOD l⁻¹ and 19 gCOD l⁻¹ in the experiments with the highest product concentrations and in the experiments with the highest yields, respectively. Shorter residence times corresponded to higher productivity. The mean HRT (hydraulic residence time) in the experiments with the highest productivities was 2.5 days. Sequencing batch reactors gave higher values of the performance variables (mean values 29 g l⁻¹, 41% COD COD⁻¹, and 12 g l⁻¹ day⁻¹ for product concentration, yield, and productivity, respectively) than processes without phase separation. Full article

Biomass-based functional rubber adsorbents were designed and prepared via inverse vulcanization and post-modification. The plant rubber was synthesized with sulfur and renewable cottonseed oil as well as various micromolecular modifiers with nitrogen-containing functional groups. Results showed that types of nitrogen-containing functional groups and dosages of modifiers had a significant impact on the adsorption capacities of the resulting polymers for Hg²⁺. Notably, when the mass ratio of 2-aminoethyl methacrylate (AEMA) to sulfur was 0.05, the resulting polymer polysulfide-co-cottonseed oil modified by AEMA (SCOA2) showed the highest adsorption capacity (343.3 mg g⁻¹) among all the prepared samples. Furthermore, the Hg²⁺ removal efficiency of SCOA2 remained over 80% of its original value after five adsorption-desorption cycles. It demonstrated a promising case for utilizing cheap industrial by-products (sulfur) and renewable materials (cottonseed oil). The prepared functional rubber provides alternative approach for mercury removal in waste utilization and sustainable chemistry. Full article

The effectiveness of polyhydroxyalkanoates (PHAs) production process from a waste stream is determined by the selection of a suitable mixed microbial culture (MMC). In this work, a feedstock from the paper industry, hardwood spent sulfite liquor (HSSL), supplemented with short-chain organic acids (SCOAs) to simulate a fermented effluent, was used as substrate to enrich a MMC in PHA-storing microorganisms. A stable culture was quickly established, and during the accumulation step the selected MMC reached a maximum PHA content of 34.6% (3HB:3HV-76:24). The bacterial community was analyzed through FISH analysis. Bacteria belonging to the four main classes were identified: Betaproteobacteria (44.7 ± 2.7%), Alphaproteobacteria (13.6 ± 1.3%) and Gammaproteobacteria (2.40 ± 1.1%) and Bacteroidetes (9.20 ± 3.8%). Inside the Betaproteobacteria class, Acidovorax (71%) was the dominant genus. Full article

In this study, we extracted fucoidan from compressional-puffing-pretreated Sargassum crassifolium by hot water. The crude extract of fucoidan (SC) was degraded by various degradation reagents and four low-molecular-weight (LMW) fucoidans, namely SCO (degradation by hydrogen peroxide), SCA (degradation by ascorbic acid), SCOA (degradation by hydrogen peroxide + ascorbic acid), and SCH (degradation by hydrogen chloride) were obtained. The degradation reagents studied could effectively degrade fucoidan into LMW fucoidans, as revealed by intrinsic viscosity, agarose gel electrophoresis, and molecular weight analyses. These LMW fucoidans had higher uronic acid content and sulfate content than those of SC. It was found that SCOA exhibited antibacterial activity. All LMW fucoidans showed antioxidant activities as revealed by DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt), and FRAP (ferric reducing antioxidant power) methods. Biological experiments showed that SC and SCOA had relatively high activity for the reversal of H₂O₂-induced cell death in 3T3-L1 adipocytes, and SCOA showed the highest effect on attenuation of lipid accumulation in 3T3-L1 adipocytes. Therefore, for the LMW fucoidans tested, SCOA showed antibacterial activity and had a high fucose content, high sulfate content, high activity for the reversal of H₂O₂-induced cell death, and a marked effect on attenuation of lipid accumulation. It can thus be recommended as a natural and safe antibacterial and anti-adipogenic agent for food, cosmetic, and nutraceutical applications. Full article

In this work, hardwood sulfite spent liquor (HSSL)—a by-product from a pulp and paper industry—was used as substrate to produce short-chain organic acids (SCOAs) through acidogenic fermentation. SCOAs have a broad range of applications, including the production of biopolymers, bioenergy, and biological removal of nutrients from wastewaters. A continuous stirred tank reactor (CSTR) configuration was chosen to impose selective pressure conditions. The CSTR was operated for 88 days at 30 °C, without pH control, and 1.76 days of hydraulic and sludge retention times were imposed. The culture required 46 days to adapt to the conditions imposed, reaching a pseudo-steady state after this period. The maximum concentration of SCOAs produced occurred on day 71—7.0 g carbon oxygen demand (COD)/L that corresponded to a degree of acidification of 36%. Acetate, propionate, butyrate, valerate, and lactate were the SCOAs produced throughout the 88 days, with an average proportion of 59:17:19:1.0:4.0%, respectively. Full article