Photobacterium marinum sp. nov., a marine bacterium isolated from a sediment sample from Palk Bay, India.

The novel, cream colored, Gram-staining-negative, rod-shaped, motile bacteria, designated strains AK15(T) and AK18, were isolated from sediment samples collected from Palk Bay, India. Both strains were positive for arginine dihydrolase, lysine decarboxylase, oxidase, nitrate reduction and methyl red test. The major fatty acids were C16:0, C18:1 ω7c, C16:1 ω7c and/or C16:1 ω6c and/or iso-C15:0 2-OH (summed feature 3). Polar lipids content of strains AK15(T) and AK18 were found to bephosphatidylethanolamine (PE), two unidentified phospholipids (PL1 and PL2) and three unidentified lipids (L1-L3). The 16S rRNA gene sequence analysis indicated strains AK15(T) and AK18 as the members of the genus Photobacterium and closely related to the type strain Photobacterium jeanii with pair-wise sequence similarity of 96.7%. DNA-DNA hybridization between strain AK15(T) and AK18 showed a relatedness of 87%. Based on data from the current polyphasic study, strains AK15(T) and AK18 are proposed as novel species of the genus Photobacterium, for which the name Photobacterium marinum sp. nov. is proposed. The type strain of Photobacterium marinum is AK15(T) (=MTCC 11066(T)=DSM 25368(T)).

Effect of substrate loading rate of chemical wastewater on fermentative biohydrogen production in biofilm configured sequencing batch reactor.

The influence of substrate loading rate on fermentative hydrogen (H2) production was studied in biofilm configured sequencing batch reactor using chemical wastewater as substrate. Reactor was operated with selectively enriched anaerobic mixed microflora at different organic loading rates (OLRs; 6.3, 7.1 and 7.9kg COD/m3 day) after adjusting the feed to a pH of 6.0 (acidophilic) to provide suitable environment for acidogenic bacterial function. Variation in H2 production rate was observed with change in OLR [specific hydrogen yield - 13.44molH2/kgCODRday (6.3kgCOD/m3day), 8.23molH2/kgCODRday (7.1kgCOD/m3 day) and 6.064molH2/kgCODR day (7.9kgCOD/m3 day)]. H2 yield showed reasonably good correlation with pH drop [6.3kgCOD/m3 day (R2 - 0.9796), 7.1kgCOD/m3 day (R2 - 0.9973), 7.9kgCOD/m3 day (R2 - 0.9908)]. Increase in OLR showed marked reduction in COD removal efficiency [22.6% - 6.3kgCOD/m3 day; 19.8% - 7.1kgCOD/m3 day and 17.2% - 7.9kgCOD/m3 day].

Biohydrogen production from chemical wastewater treatment in biofilm configured reactor operated in periodic discontinuous batch mode by selectively enriched anaerobic mixed consortia.

Molecular hydrogen (H(2)) production with simultaneous wastewater treatment was studied in biofilm configured periodic discontinuous/sequencing batch reactor using chemical wastewater as substrate. Anaerobic mixed consortia was sequentially pretreated with repeated heat-shock (100 degrees C; 2 h) and acid (pH-3.0; 24 h) treatment procedures to selectively enrich the H(2) producing mixed consortia prior to inoculation of the reactor. The bioreactor was operated at mesophilic (room) temperature (28+/-2 degrees C) under acidophilic conditions with a total cycle period of 24 h consisting of FILL (15 min), REACT (23 h), SETTLE (30 min) and DECANT (15 min) phases. Reactor was initially operated with synthetic wastewater (SW) at OLR of 4.8 kg COD/m(3)-day and subsequently operated using composite chemical wastewater (CW) at OLR of 5.6 kg COD/m(3)-day by adjusting pH to 6.0 prior to feeding to inhibit the methanogenic activity. H(2) evolution rate differed significantly with the nature of wastewater used as substrate [SW--volumetric H(2) production rate--12.89 mmol H(2)/m(3)-min and specific H(2) production rate--0.0084 mmol H(2)/min-g COD(L) (0.026 mmol H(2)/min-g COD(R)); CW--volumetric H(2) production rate--6.076 mmol H(2)/m(3)-min and specific H(2) production rate--0.0089 mmol H(2)/min-g COD(L) (0.033 mmol H(2)/min-g COD(R))]. Relatively rapid progress towards higher H(2) yield (2 h) was observed with SW compared to the CW (10 h). Substrate (COD) reduction of 32.4% (substrate degradation rate (SDR)--1.55 kg COD/m(3)-day) and 26.7% (SDR-1.49 kg COD/m(3)-day) was observed with SW and CW, respectively. The system showed rapid stabilization tendency (SW--37 days; CW--40 days) with respect to H(2) generation and COD reduction. H(2) evolution showed relatively good correlation with VFA concentration in the case of SW (R(2)-0.961) compared to CW (R(2)-0.912). A surge in pH values from 5.87 to 4.23 (SW) and 5.93 to 4.62 (CW) was observed during the cycle operation. Integration of biofilm configuration with periodic discontinuous batch operation under the defined operating conditions showed potential to influence the microbial system by selectively enriching the specific group of microflora capable of producing H(2).

Influence of recirculation on the performance of anaerobic sequencing batch biofilm reactor (AnSBBR) treating hypersaline composite chemical wastewater.

Influence of recirculation on the performance of anaerobic sequencing batch biofilm reactor (AnSBBR) was studied in the process of treating hypersaline (total dissolved inorganic solids (TDIS) approximately 26 g/l) and low biodegradable (BOD/COD approximately 0.3) composite chemical wastewater. Significant enhancement in the substrate removal efficiency and biogas yield was observed after introducing the recirculation to the system. Maximum efficiency (COD removal efficiency - 51%; SDR - 3.14 kg COD/cum-day) was observed at recirculation to feed (R/F) ratio of 2 (OLR - 6.15 kg C OD/cum-day; HLR - 2.30 cum (liquid)/cum day; UFV(A) - 0.023 m/h). Subsequent increase of R/F to 3 (OLR - 6.15 kg COD/cum-day; HLR - 3.07cum (liquid)/cum-day; UFV(A) - 0.035 m/h) resulted in reduction in COD removal efficiency (32%; SDR - 1.97 kg COD/cum-day). The enhanced performance of the system due to the introduction of recirculation was attributed to the improvement in the mass transfer between the substrate present in the bulk liquid and the attached biofilm. The hydrodynamic behavior due to recirculation mode of operation reduced the concentration gradient (substrate inhibition) of substrate and reaction by-products (VFA) resulting in mixed flow conditions.