Fermentative hydrogen and methane co-production from anaerobic co-digestion of organic wastes at high loading rate coupling continuously and sequencing batch digesters

The anaerobic co-digestion of the most abundant organic wastes was investigated for enhancing biogas production rate and quality. The used feedstock was composed of fruit and vegetable waste (FVW), waste-activated sludge (WAS), olive mill wastewater (OMW) and cattle manure (CM). A considerable methane yield of 340 L/kg volatile solid (VS) inlet was obtained using single-stage anaerobic sequencing batch reactors (ASBRs). However, VS biodegradation becomes difficult at high organic loading rate (OLR). Therefore, a continuously stirred tank reactor (CSTR) was integrated to the ASBR for waste pre-digestion. The dark fermentation leads to the improvement of organic matter solubilisation and bio-hydrogen productivity, reaching 0.73 L/L/day (H₂ content of 49.8%) when pH decreased to 5.8. Therefore, methane productivity increased from 0.6 to 1.86 L/L/day in the methanogenic reactor with a better VS biodegradation (91.1%) at high OLR. Furthermore, the bio-hythane production was performed through a controlled biogas recirculation from the dark fermentation stage into the methaniser to reach 842.4 L/kg VS inlet. The produced biogas was composed of 8% H₂, 28.5% CO₂ and 63.5% CH₄. Therefore, two-stage anaerobic co-digestion with coupled CH₄ and H₂ recuperation may be an important contribution for pollution control and high-rate bioenergy recovery (21.1 kJ/g VS inlet) from organic wastes.

Biohydrogen production from hyperthermophilic anaerobic digestion of fruit and vegetable wastes in seawater: Simplification of the culture medium of Thermotoga maritima

Biohydrogen production by the hyperthermophilic and halophilic bacterium T. maritima, using fruit and vegetable wastes as the carbon and energy sources was studied. Batch fermentation cultures showed that the use of a culture medium containing natural seawater and fruit and vegetable wastes can replace certain components (CaCl₂, MgCl₂, Balch's oligo-elements, yeast extract, KH₂PO₄ and K₂HPO₄) present in basal medium. However, a source of nitrogen and sulfur remained necessary for biohydrogen production. When fruit and vegetable waste collected from a wholesale market landfill was used, no decreases in total H₂ production (139 mmol L^-1) or H₂ yield (3.46 mol mol^-1) was observed.

Improvement of activated sludge resistance to shock loading by fungal enzyme addition during textile wastewater treatment

The effects of the additions of the fungal enzymatic extract were investigated in relation to the treatment of real textile wastewater (RTW) by the activated sludge process (ASP). The used enzyme cocktail was produced by a new isolated fungal Chaetomium globosum IMA1. The system that was operated with enzyme addition showed a better chemical oxygen demand (COD) removal efficiency (95%) compared to the control system (75%). In addition, the improvement of color removal (OD₆₂₀) efficiencies was around 15%, when the newly consortium fungal enzymes was added. As the organic loading rate (OLR) increased from 0.33 g to 0.66 g COD L^-1 d^-1, a decrease in the performance of the two reactors was observed by monitoring the quality of treated effluents. However, the ASP working with enzyme addition showed a strong resistance to shock loadings and restored after few days compared to the control system, which was strongly inhibited. In fact, the enzyme addition improved the sludge volume index (SVI) and the activity of microorganisms. A high activity of laccase (300 U.L^-1) enzyme was observed throughout the decolorization process in the improved system.

Effect of thermal pretreatment on the biogas production and microbial communities balance during anaerobic digestion of urban and industrial waste activated sludge

The effect of thermal pre-treatment on the microbial populations balance and biogas production was studied during anaerobic digestion of waste activated sludge (WAS) coming from urban (US: urban sludge) and industrial (IS: industrial sludge) wastewater treatment plants (WWTP). The highest biogas yields of 0.42l/gvolatile solid (VS) removed and 0.37l/gVS removed were obtained with urban and industrial sludge pre-treated at 120°C, respectively. Fluorescent in situ hybridization (FISH) was used to quantify the major Bacteria and Archaea groups. Compared to control trails without pretreatment, Archaea content increased from 34% to 86% and from 46% to 83% for pretreated IS and US, respectively. In fact, the thermal pre-treatment of WAS enhanced the growth of hydrogen-using methanogens (HUMs), which consume rapidly the H2 generated to allow the acetogenesis. Therefore, the stable and better performance of digesters was observed involving the balance and syntrophic associations between the different microbial populations.

Industrial textile effluent decolourization in stirred and static batch cultures of a new fungal strain Chaetomium globosum IMA1 KJ472923

The treatment of an industrial textile effluent (ITE) was investigated by using a mono-culture of a novel fungal strain Chaetomium globosum IMA1. This filamentous fungus was selected based on its capacity for dye removal via the biodegradation mechanism. The respirometric analysis showed that C. globosum IMA1 was resistant to an indigo concentration up to 700 mg equivalent COD/L. The decolourization of the ITE by C. globosum was performed in static and stirred batch systems. The better lignin peroxidase (LiP), laccase and the manganese peroxidase (MnP) productions were 829.9 U/L, 83 U/L and 247.8 U/L, respectively since 3-5 days under a stirred condition. Therefore, the chemical oxygen demand (COD) and colors (OD620) removal yields reached 88.4% and 99.8%, respectively. Fourier transforms infrared spectroscopy (FTIR) analysis of the treated effluent showed that the decolourization was due to the degradation and the transformation of dye molecules. However, spectrophotometric examination showed that the complete dye removal was through fungal adsorption (8%), followed by degradation (92%).

Microbial ecology overview during anaerobic codigestion of dairy wastewater and cattle manure and use in agriculture of obtained bio-fertilisers

The anaerobic co-digestion of dairy wastewater (DW) and cattle manure (CM) was examined and associated with microbial community's structures using Denaturing Gradient Gel Electrophoresis (DGGE). The highest volatile solids (VS) reduction yield of 88.6% and biogas production of 0.87 L/g VS removed were obtained for the C/N ratio of 24.7 at hydraulic retention time (HRT) of 20 days. The bacterial DGGE profile showed significant abundance of Uncultured Bacteroidetes, Firmicutes and Synergistetes bacterium. The Syntrophomonas strains were discovered in dependent association to H2-using bacteria such as Methanospirillum sp., Methanosphaera sp. and Methanobacterium formicicum. These syntrophic associations are essential in anaerobic digesters allow them to keep low hydrogen partial pressure. However, high concentrations of VFA produced from dairy wastes acidification allow the growth of Methanosarcina species. The application of the stabilised anaerobic effluent on the agriculture soil showed significant beneficial effects on the forage corn and tomato plants growth and crops.

An improved strategy for easy process monitoring and advanced purification of recombinant proteins

In this work, a multifunctional expression cassette, termed Multitags, combining different and complementary functionalities, was designed and used to monitor the expression and the purification of two model proteins (Pfu DNA polymerase and Myosin-VIIa- and Rab-Interracting protein : MyRIP). Multitags contains two affinity purification tags, a polyhistidine sequence (10× His) and the streptavidin-binding peptide (SBP) and as a marker tag the heme-binding domain of rat cytochrome b5 followed by the TEV cleavage site. Using the Multitags as fusion partner, more than 90 % of both fusion proteins were produced in soluble form when expressed in Escherichia coli KRX. In addition, high purity (99 %) of recombinant proteins was achieved after two consecutive affinity purification steps. The expression cassette also demonstrated an accurate monitoring capability comparable to that of a dual recognition-based method. The choice of the SBP tag was considered as an integral process that included a method for tag removal. Thus, an immobilized TEV protease fixed on streptavidin-agarose matrix was used for the cleavage of fusion proteins. After digestion, both unprocessed fusion proteins and Multitags were retained on the proteolytic column via their SBP sequence, allowing cleavage and recovery of target proteins on one step. This combined approach may accelerate the development of optimized production processes, while insuring high product quality and a low production cost.

Reprint of: A new tagged-TEV protease: Construction, optimisation of production, purification and test activity

The Tobacco Etch Virus (TEV) protease is frequently used in the cleavage of recombinant fusion proteins because of its efficiency and high specificity. In this work, we present a new recombinant form of TEV termed Streptag II-TEV for high-level production and purification of TEV protease from Escherichia coli and compare it to the hexahistidine (6xHis) tagged version of TEV. The effects of varying the host strain, the bacterial induction temperature (25, 30 and 37°C) and the IPTG inducer concentration on production and solubility of the two recombinant TEV proteases have been examined. Optimal Streptag II-TEV protein expression were obtained in the E. coli KRX strain under an induction temperature of 25°C in the presence of IPTG at 0.5mM. In these conditions, soluble Streptag II-TEV and 6xHis-TEV proteases accounted for about 25% and 18% of total soluble proteins, respectively. About 70% of Streptag II-TEV and 60% of 6xHis-TEV were detected in the supernatant. Streptag II-TEV protease purifies to near homogeneity (approximately 99%) via a simple, single step Strep-Tactin chromatography purification protocol based on the presence of Streptag II. The higher production of Streptag II-TEV coupled to its purification and cleavage efficiencies make it an attractive alternate to 6xHis-TEV.

A new tagged-TEV protease: construction, optimisation of production, purification and test activity

The Tobacco Etch Virus (TEV) protease is frequently used in the cleavage of recombinant fusion proteins because of its efficiency and high specificity. In this work, we present a new recombinant form of TEV termed Streptag II-TEV for high-level production and purification of TEV protease from Escherichia coli and compare it to the hexahistidine (6xHis) tagged version of TEV. The effects of varying the host strain, the bacterial induction temperature (25, 30 and 37°C) and the IPTG inducer concentration on production and solubility of the two recombinant TEV proteases have been examined. Optimal Streptag II-TEV protein expression were obtained in the E. coli KRX strain under an induction temperature of 25°C in the presence of IPTG at 0.5 mM. In these conditions, soluble Streptag II-TEV and 6xHis-TEV proteases accounted for about 25% and 18% of total soluble proteins, respectively. About 70% of Streptag II-TEV and 60% of 6xHis-TEV were detected in the supernatant. Streptag II-TEV protease purifies to near homogeneity (approximately 99%) via a simple, single step Strep-Tactin chromatography purification protocol based on the presence of Streptag II. The higher production of Streptag II-TEV coupled to its purification and cleavage efficiencies make it an attractive alternate to 6xHis-TEV.