Bioenergy recovery from cattle wastewater in an UASB-AF hybrid reactor.

New data on biogas production and treatment of cattle wastewater were registered using an upflow anaerobic sludge blanket-anaerobic filter (UASB-AF) hybrid reactor under mesophilic temperature conditions (37 °C). The reactor was operated in semi-continuous mode with hydraulic retention times of 6, 5, 3 and 2 days and organic loading rates of 3.8, 4.6, 7.0 and 10.8 kg CODt m-3 d-1. Biogas volumes of 0.6-0.8 m3 m-3 d-1 (3.8-4.6 kg CODt m-3 d-1) and 1.2-1.4 m3 m-3 d-1 (7.0-10.8 kg CODt m-3 d-1), with methane concentrations between 69 and 75%, were attained. The removal of organic matter with values of 60-81% (CODt) and 51-75% (CODs) allowed methane yields of 0.155-0.183 m3 CH4 kg-1 CODt and 0.401-0.513 m3 CH4 kg-1 CODs to be obtained. Volatile solids were removed in 34 to 69%, with corresponding methane yields of 0.27 to 0.42 m3 CH4 kg-1 VSremoved. The good performance of the novel hybrid reactor was demonstrated by biogas outputs higher than reported previously in the literature, along with the quality of the gas obtained in the various experimental phases. The hybrid reactor investigated in this study presents comparative advantages, particularly in relation to conventional complete mixture units, considering economic factors such as energy consumption, reactor volume and installation area.

A novel ß-xylosidase from Anoxybacillus sp. 3M towards an improved agro-industrial residues saccharification.

An intracellular ß-xylosidase (AbXyl), from the thermoalkaline Anoxybacillus sp. 3M, was purified and characterized. The homodimeric enzyme (140 kDa) was optimally active at 65 °C and pH 5.5, exhibited half life of 10 h at 60 °C, 78 and 88% residual activity after 24 h, at pH 4.5 and 8.0, respectively. Fe2+, Cu2+, Al3+, Ag+ and Hg2+ inhibited the enzyme; the activity was moderately stimulated by SDS and not influenced by ß-mercaptoethanol. In the presence of p-nitrophenyl-ß-d-xylopyranoside, AbXyl exhibited Km of 0.19 mM, Kcat of 453.29 s-1, Kcat Km-1 of 2322 s-1 mM and was moderately influenced by xylose (Ki 21.25 mM). The enzyme hydrolyzed xylo-oligomers into xylose and catalyzed transxylosilation reactions also in presence of alcohols as acceptors, producing xylo-oligosaccharides and alkyl-xylosides. Finally AbXyl was applied towards a statistically optimized process of brewery's spent grain bioconversion, highlighting the important role of this biocatalyst in reaching high yields of fermentable sugars.

Microalgae-mediated bioremediation and valorization of cattle wastewater previously digested in a hybrid anaerobic reactor using a photobioreactor: Comparison between batch and continuous operation.

Scenedesmus obliquus (ACOI 204/07) microalgae were cultivated in cattle wastewater in vertical alveolar flat panel photobioreactors, operated in batch and continuous mode, after previous digestion in a hybrid anaerobic reactor. In batch operation, removal efficiencies ranges of 65 to 70% of COD, 98 to 99% of NH4+ and 69 to 77.5% of PO4-3 after 12days were recorded. The corresponding figures for continuous flow were from 57 to 61% of COD, 94 to 96% of NH4+ and 65 to 70% of PO4-3 with mean hidraulic retention time of 12days. Higher rates of CO2 fixation (327-547mgL-1d-1) and higher biomass volumetric productivity (213-358mgL-1d-1) were obtained in batch mode. This microalgae-mediated process can be considered promising for bioremediation and valorization of effluents produced by cattle breeding yielding a protein-rich microalgal biomass that could be eventually used as cattle feed.

Wastes valorization from Rhodosporidium toruloides NCYC 921 production and biorefinery by anaerobic digestion.

Yeast production and biomass biorefinery processes for lipid and carotenoid extraction generate residues that can be used as substrates for anaerobic digestion. Glucose and carob pulp syrups were used as carbon sources to produce the yeast biomass. The yeast cultivation broth, yeast biomass residues (after carotenoid and lipid extraction) and the carob pulp solid residues obtained from the extraction of sugars were used to produce biogas by applying different Substrate/Inoculum ratios (S/I of 0.5 and 0.75). For all the residues studied, the digestions at the S/I ratio of 0.75 provided higher biogas yields than those carried out at the S/I ratio of 0.5. The best results in terms of biogas production and methane yield were observed for the yeast residue digestion at S/I of 0.75 (65.9mL, 333.7mLg-1VS-1 substrate). As monitored through flow cytometry, its bacterial consortium showed the lowest proportion of injured cells.

Energetic and biochemical valorization of cork boiling wastewater by anaerobic digestion.

BACKGROUND: In addition to energy benefits, anaerobic digestion offers other interesting advantages. The cork industry is of great environmental, economic and social significance in the western Mediterranean region, with Portugal being the world-leading producer and exporter. Cork boiling wastewater (CBW) is a toxic and recalcitrant organic effluent produced by this sector, which constitutes a serious environmental hazard. However, there is no documented research on anaerobic treatment/valorization performed with this effluent. The work presented here was developed with the aim to use the anaerobic digestion process to convert the CBW polluting organic load into an energy carrier gas and valuable molecules for industry. RESULTS: No lag phases were observed and a methane yield of 0.126 to 0.142 m(3) kg(-1) chemical oxygen demand (COD)added was registered in the mesophilic consortium experiments carried out in batch flasks at 37 ± 1°C. Anaerobic digestion can be advantageously connected to ultrafiltration or electrochemical processes, due to the following: 1) reduction of ellagic acid content and consequent decrease of CBW viscosity; and 2) increase in conductivity after the anaerobic process, avoiding the electrolyte application of the electrochemical process. The improvement of several CBW biochemical features shows that anaerobic digestion may provide additionally useful molecules. The rise in concentration of some of these compounds, belonging to the benzoic acid family (gallic, protocatechuic, vanillic and syringic acids), is responsible for the increase of antiradical activity of the phenolic fraction. Additionally, some enzymatic activity was also observed and while the laccase activity increased in the digested effluent by anaerobiosis, xylanase was formed in the process. CONCLUSIONS: The multidisciplinary approach adopted allowed the valorization of CBW in terms of energy and valuable biomolecules. By exploiting the anaerobic digestion process potential, a novel methodology to toxic and recalcitrant cork processing wastewater was developed.