Dark fermentative biohydrogen production from vinicultural biomass without exogenous inoculum in a semi-batch reactor: A kinetic study.

This work employed a unique kind of vinicultural biomass (grape residues) to generate fermentative hydrogen. This form of biomass serves two purposes (contains substrate and inoculum). Four mathematical model methods were established; these models were used to represent the fluctuation of hydrogen generation and other fermentation products (organic acids, alcohols), the consumption of substrates included in biomass, and bacterial growth. One of these models was verified using experimental data and used to represent all of the metabolic pathways of bacteria contained in the medium and the interaction between products and substrates. The optimal biomass load, 60 g COD (Chemical Oxygen Demand)/L with a concentration of 0.22 mol of hexose and 0.0444 mol of tartrate offers the best hydrogen yield.

Unexpected high production of biohydrogen from the endogenous fermentation of grape must deposits.

The aim of this work was to assess the performances of wine byproduct biomass for hydrogen production by dark fermentation. Grape must deposits from two grape varieties (Pinot Gris and Chardonnay) were considered, either with external microbial inoculum or without. We show that grape must residues contain endogenous microflora, well adapted to their environment, which can degrade sugars (initially contained in the biomass) to hydrogen without any nutrient addition. Indeed, hydrogen production during endogenous fermentation is as efficient as with an external heat-treated inoculum (2.5 ± 0.4 LH2.L-1reactor and 1.61 ± 0.41 molH2.mol-1consumed hexose, respectively) with a lower energy cost. Hydrogen-producing bacteria were selected from the endogenous microflora during semi-batch bioreactor operation, as shown by T-RFLP profiles and 16S rRNA sequencing, with Clostridium spp. (butyricum, beijerinckii, diolis, roseum) identified as the major phylotype. Such hydrogen production efficiency opens new perspectives for innovating in the valorization of winery by-products.

Biohydrogen production in a continuous liquid/gas hollow fiber membrane bioreactor: Efficient retention of hydrogen producing bacteria via granule and biofilm formation.

The aim of this work was to develop a continuous liquid/gas membrane bioreactor (L/G MBR), i.e. a fermenting module including hollow fibers membrane for L/G separation, for biohydrogen production by dark fermentation. Originally seeded with sludge from a wastewater treatment plant, the L/G MBR underwent a complete stop for eight months. It was then operated without further reseeding. In the present experiment, performed 551 days after the last reseeding, average hydrogen yield of 1.1 ± 0.2 mol per mol glucose added and hydrogen productivity of 135 ± 22 mL/L/h were reached, with acetate and butyrate as the main metabolite products. DNA sequence analysis revealed that Clostridium beijerinckii, Clostridium pasteurianum and Enterobacter sp. were dominant in liquid outlet, in a biofilm on the surface of the hollow fibers and in microbial granules. The L/G MBR has potential for the concentration and the long-term maintenance of an active hydrogen-producing bacterial community without need for reseeding.

Detection of 1-hydroxypyrene in urine by direct fluorometric analysis on a solid sorbing phase. Validation and application of the method to biological monitoring of PAH-exposed persons.

A new method for the detection and quantification of 1-hydroxypyrene (1-OHPy) in the urines of persons exposed to polycyclic aromatic hydrocarbons (PAH) has been evaluated. The method is based on extraction/concentration of the analyte onto a small element cut into tabs from an extraction disk (ENVI-Disk trade mark C18 from Supelco) combined with front-face synchronous fluorescence detection and direct quantification on the solid sorbent element. The limit of detection for 1-OHPy was estimated to be about 0.03-0.04 micro g/L, a value which is significantly lower than the pyrene metabolite concentration commonly found in unexposed to weakly PAH-exposed persons ( approximately 0.1-0.3 micro g/L). A quantification based on only one standard addition has been adopted and the method was validated both by testing analyte recovery using a known amount of a commercially available pyrene metabolite and by comparing the results with those obtained by high-performance liquid chromatography (HPLC). The results were very close to the HPLC results, the largest deviations being attributed to variations or defects in the stirring system, the rate stability of which was found to be of major importance for the reproducibility and reliability of the measurements. The applicability of the method was further tested by analyzing 1-OHPy in the urine of a volunteer exposed to various automobile traffic zones. The results confirm previous findings which lead to the conclusion that urinary concentrations of PAH metabolites are influenced more by smoking habit than by exposure to urban atmospheric pollution. Thus, the method appears to be an alternative to the usual method based on HPLC. Moreover it presents some advantages, being simple to operate and requiring relatively low-cost instruments.