Hydrogen energy, as a kind of clean energy with great potential, has been a hotspot for study worldwide. Based on the recent research on biohydrogen production, this paper gives a brief review on the following aspects: fermentative hydrogen production process and the engineering control statagy, key factors affecting the efficiency of hydrogen production, such as substrates, cysteine, metal ions, anaerobic fermentation terminal products, and formic acid and ammonia. Moreover, anaerobic fermentative hydrogen-producing strain and regulation and control of enzyme gene in fermentative hydrogen production are also discussed. Finally, the prospect of anaerobic fermentative biohydrogen production is proposed in three study areas, namely developing new techniques for breeding hydrogen-producing bacteria, exploitations of more strains and gene resources, and intensifying the application of microbial molecular breeding in hydrogen production.

Recent advances in fermentative biohydrogen production

Aerobic granular sludge was cultivated by using di erent kinds of seed sludge in sequencing batch airlift reactor. The influence of seed sludge on physical and chemical properties of granular sludge was studied; the microbial community structure was probed by using scanning electron microscope and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The results showed that seed sludge played an important role on the formation of aerobic granules. Seed sludge taken from beer wastewater treatment plant (inoculum A) was more suitable for cultivating aerobic granules than that of sludge from municipal wastewater treatment plant (inoculum B). Cultivated with inoculum A, large amount of mature granules formed after 35 days operation, its SVI reached 32.75 mL/g, and SOUR of granular sludge was beyond 1.10 mg/(g min). By contrast, it needed 56 days obtaining mature granules using inoculum B. DGGE profiles indicated that the dominant microbial species in mature granules were 18 and 11 OTU when inoculum A and B were respectively employed as seed sludge. The sequencing results suggested that dominant species in mature granules cultivated by inoculum A were Paracoccus sp., Devosia hwasunensi, Pseudoxanthomonas sp., while the dominant species were Lactococcus ra nolactis and Pseudomonas sp. in granules developed from inoculum B.

/pdf/effect-of-seed-sludge-on-characteristics-and-microbial-5514jbuvgz.pdf

Effect of seed sludge on characteristics and microbial community of aerobic granular sludge.

Phytoplankton are the primary producers at the basis of aquatic food webs, and bacteria play an important role in energy flow and biochemical cycling in aquatic ecosystems. In this study, both the bacterial and phytoplankton communities were examined in the oligotrophic Lake Basomtso and the eutrophic Lake South (China). The results of this study showed that the phytoplankton density and diversity in the eutrophic lake were higher than those in the oligotrophic lake. Furthermore, Chlorophyta (68%) and Cryptophyta (24%) were the dominant groups in the eutrophic lake, while Bacillariophyta (95%) dominated in the oligotrophic lake. The bacterial communities in the waters and sediments of the two lakes were mainly composed of Proteobacteria (mean of 32%), Actinobacteria (mean of 25%), Bacteroidetes (mean of 12%), and Chloroflexi (mean of 6%). Comparative analysis showed that the abundance of bacteria in the eutrophic lake was higher than that in the oligotrophic lake (p < 0.05), but the bacterial diversity in the oligotrophic lake was higher than that in the eutrophic lake (p < 0.05). Finally, the bacterial abundance and diversity in the sediments of the two lakes were higher than those in the water samples (p < 0.05), and the Latescibacteria and Nitrospinae groups were identified only in the sediments. These results suggest that both the phytoplankton and bacterial communities differed considerably between the oligotrophic lake and the eutrophic lake.

https://www.mdpi.com/2076-2607/7/12/621/pdf

Phytoplankton and Bacterial Community Structure in Two Chinese Lakes of Different Trophic Status.

The conversion of glucose to hydrogen was evaluated using continuous stirred tank reactor at pH 5.5 with various hydraulic retention times (HRT) at 30 degrees C. Furthermore, the population dynamics of hydrogen-producing bacteria was surveyed by fluorescence in-situ hybridization using probe Clost IV targeting the genus Clostridium based on 16S rRNA. It was clear that positive correlation was observed between the cells quantified with probe Clost IV and hydrogen yield of the respective sludge. The numbers of hydrogen-producing bacteria were decreased gradually with increasing HRT, were 9.2 x 10(8), 8.2 x 10(8), 2.8 x 10(8), and 6.2 x 10(7) cell/mL at HRT 6, 8, 12, and 14 h, respectively. The hydrogen yield was 1.4-1.5 mol H2/mol glucose at the optimum HRT range 6-8 h. It is considered that the percentage of the hydrogen-producing bacteria to total bacteria is useful parameter for evaluation of hydrogen production process.

Effect of hydraulic retention time on the hydrogen yield and population of Clostridium in hydrogen fermentation of glucose.

The invention discloses a culture method of municipal sewage nitrosification granule sludge, belonging to the field of restoration and regeneration of an aquatic environment. The invention aims to solve the problems of low carbon-nitrogen ratio, low denitrification efficiency and waste of abundant energy sources in the municipal sewage. The method comprises steps: anaerobic ammoxidation granule sludge is inoculated in an SBR (sequencing batch reactor); by using domestic sewage as raw water, the dissolved oxygen in the reactor is controlled at 4 mg/L or more, the stirring speed is controlled at 100 r/min, the temperature is controlled at 30 DEG C, the hydraulic retention time is controlled at 8 hours, and the sedimentation time is controlled at 5 minutes; the aerobic ammoxidation bacterium AOB and denitrifying bacterium can form granule sludge with anaerobic ammoxidation granule sludge as core; the shearing force generated by aeration can provide selection pressure for the formation of the granule sludge and promote the formation of the granule sludge; and the short sedimentation time is beneficial to elimination of nitrobacteria, thereby keeping the nitrosification stable. By using the method, the ammonia nitrogen removal ratio is up to 100%, and the nitrogen accumulation rate is higher than 95%.

Culture method of aerobic nitrosification granule sludge

Disclosed is a culture method of aerobic nitrosated granular sludge comprising the steps of, loading active sludge into upstream type aerobic reactor equipped with three-phase separator, letting in simulated waste water with an amino-nitrogen concentration of 200-800mg/L and right amount of added phosphate and trace element, flowing the waste water through sludge and exiting from the upper portion of the reactor, employing air aeration with air speed of 20-50L/h, controlling reactor temperature, pH, dissolved oxygen and conditions including waterpower retention period.

Culture method of aerobic nitrosated granular sludge

Four methanogenic granules taken from an anaerobic reactor in different periods were investigated by FISH and DGGE, the eubacterial and archaeal community in these granules was researched and the phylogenetic analysis of dominant archaea was also studied. The FISH results indicated that the quantity of eubacteria was much more than archaea in the methanogenic granule and most eubacteria were located in the out layer of granule, while most archaea were located in the inner layer. The DGGE fingerprints indicated that as the organic loading rate of the reactor increased and the operating time elapsed, the eubacterial community was kept stable relatively, while the archaeal community was changed significantly, which resulted in the gradual decrease of the archaeal varieties. As seven typical bands were cut and sequenced, the results indicated that the dominant species of archaea in granule of the last period were Methanocor pusculum, Methanobacterium, Methanosaeta, and etc.

Study on microbial community in methanogenic granular sludge by FISH and DGGE

Anaerobic biological hydrogen productions were achieved successfully in two lab-scale anaerobic hydrogen production reactors under mesophilic (37 degrees C) and thermophilic (55 degrees C) conditions, respectively. The mesophilic reactor, a CSTR, was operated over 4 months by seeding with river sediments and feeding with glucose solution, in which the highest hydrogen production rate was 8.6 L/(L x d) and the substrate hydrogen production molar ratio (H2/glucose) was 1.98. After seeded with anaerobic methanogenic granules, a UASB reactor was thermophilically operated by feeding with sucrose solution and during its steady operation period, the hydrogen production rate was 6.8 L/(L x d) and the substrate hydrogen production molar ratio (H2/sucrose) was 3.6. Within the produced gas, the H2 percentages were about 43% and others were CO2, no methane could be detected. Thermophilic hydrogen-producing granules were successfully cultivated in the UASB reactor, which were grey-white in color, the diameters were about 0.8 - 1.2 mm, and typical settling velocities were about 30 - 40 m/h. Through SEM a great number of bacilli could be found on the surface of the granules which made the surface rough. Total DNA of these two hydrogen production sludges were extracted and purified, and the PCR and DGGE process were conducted, the results indicate that most of the eubacteria in two sludges are the same, but the dominant species are obviously different with each other.

Continuous Bio-Hydrogen Production by Mesophilic and Thermophilic Cultures

By using a lab-scale aerated upflow sludge bed reactor, the inoculated anaerobic granule was cultivated to aerobic nitrification granule, and then converted to short-cut nitrification granule with the short-cut nitrification efficiencies above 90%. Appling real-time quantity PCR, and florescent in situ hybridization techniques, the ecological community structure of nitrification bacteria in aerobic granules were studied. The results show that there existed a layered structure in the aerobic granule, the ammonia oxidizing bacteria (AOB) was mainly located in the surface area of the granule, and the nitrite oxidizing bacteria (NOB) was mainly located in the inner area of the granule, was just adjacent to the AOB. There was no active bacteria in the inner core area. The amount of AOB in the granules increased, as the ammonia loading rate of the reactor was increased gradually. The percentage of AOB in the total amount of Eubacteria in the granule was 0.45%, 5.20%, 15.37%, 48.55% respectively, as the ammonia loading rate of the reactor were 0, 0.4, 1.0 and 2.2 kg/(m3 x d) respectively, and the nitrosofication efficiency were 0%, 35%, 50%, 99% relatively.

Jian-E Zuo

Papers

Culture method of aerobic nitrosated granular sludge

Study on microbial community in methanogenic granular sludge by FISH and DGGE

Continuous Bio-Hydrogen Production by Mesophilic and Thermophilic Cultures

[Community structure of nitrification bacteria in aerobic short-cut nitrification granule].