Brewing of glucuronic acid-enriched apple cider with enhanced antioxidant activities through the co-fermentation of yeast (Saccharomyces cerevisiae and Pichia kudriavzevii) and bacteria (Lactobacillus plantarum)

Co-fermentation using yeast (Saccharomyces cerevisiae and Pichia kudriavzevii) and the bacteria (Lactobacillus plantarum) as starters isolated from spontaneous sourdough was conducted for the brewing of glucuronic acid (GlcA)-enriched apple cider. The concentration of GlcA in the apple cider co-fermented for 14 d with commercial S. cerevisiae and L. plantarum was 37.7 ± 1.7 mg/mL while a concentration of 62.8 ± 3.1 mg/mL was recorded for fermentation with P. kudriavzevii and L. plantarum, which was higher than the corresponding single yeast fermentation. The co-fermented apple cider revealed higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of 171.67 ± 0.79 µg trolox equivalents (TE)/mL using P. kudriavzevii and L. plantarum, compared to the control (143.89 ± 7.07 µg TE/mL) just using S. cerevisiae. Thus, the co-fermentation of S. cerevisiae and L. plantarum and P. kudriavzevii and L. plantarum provided a new strategy for the development of GlcA-enriched apple cider with enhanced antioxidant capacity.     

Co-fermentation of sewage sludge and algae and Fe2+ addition for enhancing hydrogen production

Co-fermentation of sewage sludge and algae was performed for enhancing the hydrogen production, and the effect of Fe²⁺ on co-fermentation process was examined. Results showed that both co-fermentation process and Fe²⁺ addition promoted hydrogen production. Highest hydrogen production of 28 mL/100 mL (14.8 mL H₂/g VS_added) was obtained from the co-fermentation group with 600 mg/L Fe²⁺ addition, which was 2.15 times, 2.00 times and 1.87 times of mono-fermentation of sludge, mono-fermentation of algae, and the co-fermentation group without Fe²⁺ addition. Both volatile solids and protein degradation were stimulated by co-fermentation process. Microbial analysis showed that co-fermentation groups with Fe²⁺ addition enriched Clostridium sensu stricto 13, Clostridium tertium and Terrisporobacter, which were positively correlated with cumulative hydrogen production. This study suggested that the co-fermentation of sludge and algae in the presence of Fe²⁺ could significantly improve the hydrogen production by stimulating the hydrogen-producing metabolism.     

Different ratios of carbon sources in the fermentation of cheese whey and glucose as substrates for hydrogen and ethanol production in continuous reactors

The fermentation of glucose, cheese whey and the mixture of glucose and cheese whey were evaluated in this study from two inocula sources (sludge from a UASB reactor for swine wastewater treatment and poultry slaughterhouse) for hydrogen production in continuous anaerobic fluidized bed reactors (AFBR). For all fermentations, a hydraulic retention time (HRT) of 6 h and a substrate concentration of 5 g COD L⁻¹ were used. In glucose fermentation, the maximum hydrogen yield (HY) was 1.37 mmol H₂ g⁻¹ COD. The co-fermentation of the cheese whey and glucose mixture was favorable for the concomitant production of hydrogen and ethanol, with yields of up to 1.7 mmol H₂ g⁻¹ COD and 3.45 mol EtOH g⁻¹ COD in AFBR2. The utilization of cheese whey as a sole substrate resulted in an HY of 1.9 mmol H₂ g⁻¹ COD. Throughout the study, ethanol fermentation was evident.     

Urban lignocellulosic biomass can significantly contribute to energy production in municipal wastewater treatment plants – A GIS-based approach for a metropolitan area

The common fermentation of biogenic wastes and sewage sludge in digesters of municipal wastewater treatment plants is a technically feasible and economically viable approach. As the number of rural biogas production sites is steadily increasing, the question has been raised which biomass feedstocks are left available in sufficient quantities to be used for energy generation at wastewater treatment plant level. The contribution of lignocellulosic biomass collected from urban areas is generally neglected within this context. In the present study, 24 urban substrates have been analyzed for their theoretical methane potential, while 13 of them were tested in batch assays for the determination of their practical achievable methane yield. The theoretical evaluation of the methane potential yielded values ranging between 0.393 and 0.576 Nm³ kgVS⁻¹. The methane yields obtained by batch assays showed significantly lower yields, which depends on the individual composition of the substrates in terms of lignin, hemicellulose and cellulose. A GIS spatial analysis for the Rhine-Ruhr metropolitan area was performed to evaluate the feasible capacity of urban biomass as co-fermentation feedstock in digesters of municipal wastewater treatment plants. The analysis revealed that green urban areas provide a significant quantity of biomass of 377 t_FM d⁻¹ that could cover 67% of the annual energy demand of twelve typical wastewater treatment plants located in the metropolis.     

Co-fermentation of carbohydrates and proteins for biohydrogen production: Statistical optimization using Response Surface Methodology

In this study, the co-fermentation of carbohydrates and proteins at different ratios (C1–C5) was explored. The rates of particulate carbohydrates degradation in the co-substrate mixtures, not only increased with starch concentrations, but negatively impacted the degradation rates of the particulate proteins. Particulate proteins also negatively impacted particulate carbohydrate degradation rates, albeit to a lesser extent. Generally, there was a synergistic impact on hydrogen production and the optimum ratio that required no pH control occurred at C4 (80% carbohydrates + 20% proteins) with a hydrogen yield of 350 mL H₂/gCOD_added which was 38% higher than the expected, and the fermentation followed the acetate-ethanol pathway. Response Surface Methodology (RSM) was used to optimize the responses to the co-fermentation process at C4. By fitting 20 experimental data points, the responses adequately fitted second-order polynomial models. At the optimized VFA and ammonia concentrations of 580 mg/L and 40 mg/L, respectively, the biohydrogen production process would be feasible without pH control at a carbohydrate-to-protein COD ratio of 4:1.     

Impact of acetic acid in methane production from glycerol/acetic acid co-fermentation

Co-fermentation of glycerol and acetic acid in anaerobic digestion was set up to generate biogas in batch reactors under mesophilic condition, pH 7. The experiments were varied COD ratios of glycerol and acetic acid were varied with the total combined COD of 5,20 0 mg/L. The maximum methane yield was obtained from glycerol/acetic acid ratio of 6:4. The cumulative methane, production rate and lag phase were 240 mL, 14 mL hr⁻¹, and 11 hr. The research indicated acetic acid boosted methane production when it was co-fermented with glycerol.     

The effects of seed sludge and hydraulic retention time on the production of hydrogen from a cassava processing wastewater and glucose mixture in an anaerobic fluidized bed reactor

The potential for co-fermentation of a cassava processing wastewater and glucose mixture was studied in anaerobic fluidized bed reactors. The effects of different hydraulic retention times (HRTs) (10–2 h) and varying sources of inoculum are reported. The sludge from a UASB reactor that had been used to treat poultry slaughterhouse wastewater (SP) resulted in the highest yields of hydrogen (HY) and ethanol (EtOHY) of 1.0 mmol H₂ g⁻¹ COD (10 h) and 3.0 mmol EtOH g⁻¹ COD (6 h). The sludge from a UASB reactor used for the treatment of swine wastewater (SW) resulted in a maximum HY of 0.65 mmol H₂ g⁻¹ COD (6 h) and EtOHY of 2.1 mmol g⁻¹ COD (10 and 8 h). Methane was produced with a maximum production of 9.68 L CH₄ d⁻¹ L⁻¹. Based on phylogenetic analysis of 16S rRNA, bacteria and methanogenic archaea similar to Lactobacillus and Methanobacterium, respectively, were identified.     

纤维废渣固态酒精发酵及纤维素－淀粉共发酵的研究

本文对造纸厂纤维废渣固态酒精发酵工艺进行了研究。试验结果显示，利用纤维素酶曲和酒精活性干酵母，采用固态同步糖化发酵工艺和补料技术，在滤纸酶活用量为２０ＩＵ／ｇ底物、加水比为４，３５℃条件下，酒醅酒度可达５．１（Ｖ／Ｗ），造纸厂细杂纤维的酒精得率为０．１７（Ｗ／Ｗ）。在废渣中添加一定量的玉米粉，利用纤维素酶曲中的淀粉酶活性进行纤维素－淀粉共发酵，可使酒醅酒度提高到８．７％（Ｖ／Ｗ）。     

纤维废渣固态酒精发酵及纤维素－淀粉共发酵的研究

本文对造纸厂纤维废渣固态酒精发酵工艺进行了研究。试验结果显示，利用纤维素酶曲和酒精活性干酵母，采用固态同步糖化发酵工艺和补料技术，在滤纸酶活用量为２０ＩＵ／ｇ底物、加水比为４，３５℃条件下，酒醅酒度可达５．１（Ｖ／Ｗ），造纸厂细杂纤维的酒精得率为０．１７（Ｗ／Ｗ）。在废渣中添加一定量的玉米粉，利用纤维素酶曲中的淀粉酶活性进行纤维素－淀粉共发酵，可使酒醅酒度提高到８．７％（Ｖ／Ｗ）。     

Co-fermentation of a mixture of glucose and xylose to hydrogen by Thermoanaerobacter thermosaccharolyticum W16: Characteristics and kinetics

Glucose and xylose co-fermentation is crucial to maximize hydrogen yield from waste lignocellulose. In this study, cell growth, sugar consumption, and hydrogen production profiles of Thermoanaerobacter thermosaccharolyticum W16 feeding with a range of glucose and xylose were experimental investigated coupled with kinetic analysis. Results showed although T. thermosaccharolyticum W16 could use both glucose and xylose for hydrogen production, a maximum cell growth rate of 0.27 g/L/h and hydrogen production rate of 14.53 mmol/L/h was found with glucose as sole substrate, the value was 92.8% and 49.8% higher than using xylose as the only carbon source. Further interpolation analysis and experimental demonstration suggested when glucose content in the mixed substrate higher than 58.2%, the inhibitory effect on xylose utilization was increased, but when glucose concentration fell below 21.7%, its utilization will be subject to a certain degree of feedback inhibition. Coupling experimental results with kinetic analysis in this study provides a powerful evidence to further develop the potential of T. thermosaccharolyticum W16 as a biocatalyst for hydrogen production from lignocellulosic biomass.