Feasibility of biohydrogen production from industrial wastes using defined microbial co-culture

BACKGROUND: The development of clean or novel alternative energy has become a global trend that will shape the future of energy. In the present study, 3 microbial strains with different oxygen requirements, including Clostridium acetobutylicum ATCC 824, Enterobacter cloacae ATCC 13047 and Kluyveromyces marxianus 15D, were used to construct a hydrogen production system that was composed of a mixed aerobic-facultative anaerobic-anaerobic consortium. The effects of metal ions, organic acids and carbohydrate substrates on this system were analyzed and compared using electrochemical and kinetic assays. It was then tested using small-scale experiments to evaluate its ability to convert starch in 5 L of organic wastewater into hydrogen. For the one-step biohydrogen production experiment, H1 medium (nutrient broth and potato dextrose broth) was mixed directly with GAM broth to generate H2 medium (H1 medium and GAM broth). Finally, Clostridium acetobutylicum ATCC 824, Enterobacter cloacae ATCC 13047 and Kluyveromyces marxianus 15D of three species microbial co-culture to produce hydrogen under anaerobic conditions. For the two-step biohydrogen production experiment, the H1 medium, after cultured the microbial strains Enterobacter cloacae ATCC 13047 and Kluyveromyces marxianus 15D, was centrifuged to remove the microbial cells and then mixed with GAM broth (H2 medium). Afterward, the bacterial strain Clostridium acetobutylicum ATCC 824 was inoculated into the H2 medium to produce hydrogen by anaerobic fermentation. RESULTS: The experimental results demonstrated that the optimum conditions for the small-scale fermentative hydrogen production system were at pH 7.0, 35°C, a mixed medium, including H1 medium and H2 medium with 0.50 mol/L ferrous chloride, 0.50 mol/L magnesium sulfate, 0.50 mol/L potassium chloride, 1% w/v citric acid, 5% w/v fructose and 5% w/v glucose. The overall hydrogen production efficiency in the shake flask fermentation group was 33.7 mL/h-1.L-1, and those the two-step and the one-step processes of the small-scale fermentative hydrogen production system were 41.2 mLVh-1.L-1 and 35.1 mL/h-1.L-1, respectively. CONCLUSION: Therefore, the results indicate that the hydrogen production efficiency of the two-step process is higher than that of the one-step process.

Cell volume regulation in the perfused liver of a freshwater air-breathing cat fish Clarias batrachus under aniso-osmotic conditions: roles of inorganic ions and taurine.

The roles of various inorganic ions and taurine, an organic osmolyte, in cell volume regulation were investigated in the perfused liver of a freshwater air-breathing catfish Clarias batrachus under aniso-osmotic conditions. There was a transient increase and decrease of liver cell volume following hypotonic (-80 mOsmol/l) and hypertonic (+80 mOsmol/l) exposures,respectively, which gradually decreased/increased near to the control level due to release/uptake of water within a period of 25-30 min. Liver volume decrease was accompanied by enhanced efflux of K+ (9.45 +/- 0.54 micromol/g liver) due to activation of Ba(2+)- and quinidine-sensitive K(+) channel, and to a lesser extent due to enhanced efflux of Cl(-) (4.35+/- 0.25 micromol/g liver) and Na+ (3.68+/- 0.37 micromol/g liver). Conversely, upon hypertonic exposure, there was amiloride-and ouabain-sensitive uptake of K+ (9.78+/- 0.65 micromol/g liver), and also Cl(-) (3.72 +/- 0.25 micromol/g liver).The alkalization/acidification of the liver effluents under hypo-/hypertonicity was mainly due to movement of various ions during volume regulatory processes. Taurine,an important organic osmolyte, appears also to play a very important role in hepatocyte cell volume regulation in the walking catfish as evidenced by the fact that hypo- and hyper-osmolarity caused transient efflux (5.68 +/- 0.38 micromol/g liver) and uptake (6.38 +/- 0.45 micromol/g liver) of taurine, respectively. The taurine efflux was sensitive to 4,4' -di-isothiocyanatostilbene-2,2'-disulphonic acid (DIDS, an anion channel blocker), but the uptake was insensitive to DIDS, thus indicating that the release and uptake of taurine during volume regulatory processes are unidirectional. Although the liver of walking catfish possesses the RVD and RVI mechanisms, it is to be noted that liver cells remain partly swollen and shrunken during anisotonic exposures,thereby possibly causing various volume-sensitive metabolic changes in the liver as reported earlier.

Does melatonin have a time-dependent effect on brain and gill ionic metabolism in a teleost, Anabas testudineus (Bloch)?

Exogenous administration of 0.20, 0.40 and 0.60 microg/g body weight melatonin over a 24 hr cycle caused an inhibition of Na+, K+ ATPase activity in both brain and gills of A. testudineus. However, Ca2+ ATPase activity in the brain was significantly inhibited by the highest dose, and that in the gill at all the doses of melatonin. Evening injection of melatonin had an inhibitory effect on both brain and gill Na+ K+ and Ca2+ ATPase activity. Melatonin treatment in the morning for 12 hrs did not have an effect on brain Na+, K+ ATPase, while Ca2+ ATPase was inhibited. Similar treatment stimulated Na+, K+ and Ca2+ ATPase activity in the gills. Sodium, potassium and calcium ions in the gill were significantly reduced in the evening treated group while no change was observed in the morning melatonin injected group. The results suggest that melatonin elicits a time-dependent effect on the enzymes and ionic content in the brain and gills of A. testudineus.

Insulin regulates ionic metabolism in a fresh water teleost, anabas testudineus (bloch).

Short term effects of insulin on total brain and branchial Na+K+ ATPase, Ca2+ ATPase and Na+, K+ and Ca2+ ions were investigated in A. testudineus. The increase in brain Ca2+ ATPase after alloxan treatment may account for an increased amount of intracellular calcium required for biochemical events taking place inside the cells. Branchial Na+K+ATPase was significantly stimulated while Ca2+ ATPase significantly inhibited after alloxan treatment. This suggests that alloxan exerts its inhibitory effect on the ATP-driven Ca2+ transport via; its action on the Ca2+ pump protein rather than the membrane permeability to Ca2+. The increased activity of brain Na+K+ ATPase at 3 and 24 hr by insulin to alloxan pretreated fish may account for the stimulated co-transport of glucose and its utilization for energy requirements and the excitatory action on neurons in the brain. The elevated brain Ca2+ ATPase may be due to the role of calcium as a second messenger in hormone action. At 24 hr, the activity of branchial Na+K+ ATPase and Ca2+ ATPase in alloxan pretreated specimens was significantly stimulated by insulin. This may be due to increased synthesis of these enzyme units. Administration of insulin (lU/fish) in normal fish significantly inhibited the activity of brain and branchial Na+K+ ATPase while brain Ca2+ ATPase showed a stimulatory effect at 3 and 24 hr compared to control. Inhibition of total branchial Ca2+ ATPase activity by insulin may be due to increased Ca2+ concentration. Higher plasma glucose level in alloxan treated groups confirms the diabetic effect of alloxan. Insulin reverses this effect. The possible mechanism by which insulin controls Na+K+ ATPase activity appears to be tissue specific. The results seem to be the first report on the effect of insulin on ATPase activity in a teleost. These data are consistent with the hypothesis that insulin performs a role in hydro mineral regulation in freshwater teleosts.

Effect of sensitization on membrane ion fluxes & intracellular calcium in guineapigs.

BACKGROUND & OBJECTIVES: The biochemical mechanisms underlying the development of sensitization-induced airway hyperresponsiveness (AHR) in asthma are poorly defined. Alterations in the regulation of intracellular calcium may play an important role in its pathogenesis. We carried out this study to see the effect of sensitization with ovalbumin on membrane ion fluxes and intracellular calcium in a guinea pig model. METHODS: Airway reactivity to inhaled histamine was measured initially and after sensitization with ovalbumin in 28 guineapigs. Intracellular calcium [Ca(2+)]i was measured in tracheal smooth muscle cells and peripheral leukocytes using fluorescent dye FURA 2AM. Calcium and sodium ion influx across the cell membrane was measured in leukocytes. Ouabain-sensitive Rubidium ((86)Rb) influx was measured in tracheal smooth muscles cells. The activities of Na(+), K(+) ATPase and Ca(2+) ATPase were measured in tracheal smooth muscle cells. Lipid peroxides were measured in plasma. RESULTS: Airway responsiveness was significantly (P<0.001) increased after sensitization along with an increase in [Ca2+]i levels in leukocytes and tracheal smooth muscle cells, higher rates of (45)Ca and (22)Na influx in leukocytes and higher (86)Rb influx rates in tracheal smooth muscle cells, and increased levels of lipid peroxides in plasma. INTERPRETATION & CONCLUSION: In guineapig model of asthma sensitization to allergen increased the membrane permeability to calcium and sodium, and intracellular calcium levels. These alterations may play a role in the pathogenesis of airway hyper-responsiveness following sensitization.

Prospects of plasma immersion ion implantation and deposition (PIlI & D) in the biomaterials field in Malaysia and south East Asia

One of the emerging technologies in the area of plasma processing is plasma immersion ion implantation (PSII). The paper addresses the merits offered by the PSII technique especially in the area of biomaterial processing. Worldwide development status as well as the drive towards commercial applications is elaborated in an attempt to draw the attention to the importance of the process for Malaysia as well as south East Asia.