Masayoshi Morimoto

Hydrogen production from industrial wastewater by anaerobic microflora in chemostat culture

Abstract Continuous production of hydrogen from sugary wastewater by anaerobic microflora in chemostat culture was examined as a function of hydraulic retention time (HRT) in the reactor. The measured volumes of the evolved gas at each HRT were almost constant (Avg. 3590 ml/l-feed) and the composition of the gas was approximately 64% hydrogen, 36% carbon dioxide, and less than 0.13% methane. Steady states on evolution of gas were observed for 190 d at HRTs from 0.5 to 3 d giving hydrogen production rates from 198 to 34 mmol/l/d. Significant amounts of acetate and butyrate were formed as by-products. A maximum production yield of hydrogen of 14 mmol/g carbohydrate removed was obtained at an HRT of 0.5 d. The maximum removal efficiency of carbohydrates was approximately 97% at an HRT of 3 d. The patterns of fermentation by anaerobic microflora changed with HRT, i.e., acid formation decreased with decreasing HRT.

Biological production of hydrogen from cellulose by natural anaerobic microflora

The capability of natural anaerobic microflora to produce hydrogen was examined with artificial wastewater containing cellulose. The microflora in sludge compost was found to produce a significant amount of hydrogen (2.4 mol/mol-hexose). Among the fermentation products other than hydrogen and carbon dioxide, the lower fatty acids, mainly acetate and butyrate, constituted more than approximately 90% of the total soluble metabolites.

Efficient hydrogen production from starch by a bacterium isolated from termites

Abstract Clostridium beijerinckii AM21B strain was isolated from termites. AM21B respectively converted 10 g of glucose or starch to 2,450 ml or 2,255 ml of H 2 , while the maximum evolution rate was 660 ml or 410 ml of H 2 per hour, respectively from 1 l of PY medium containing 10 g of glucose or starch, at pH 6.5. This H 2 production from starch by a non-photosynthetic bacterium appears to be the first report known to the authors.

Effect of amylase accumulation on hydrogen production by Clostridium beijerinckii, strain AM21B

Abstract The maximal enzymatic activity of crude amylase produced in the batch culture of Clostridium beijerinckii strain AM21B grown in PY medium with starch was obtained at 55°C and in an acidic pH range of 4.6 to 5.4. Amylase was produced in the culture medium after 4 h (46.6 units) and reached a peak (405.5 units) after 12 h cultivation at 36°C, pH 6.0. Although the most efficient production of amylase, hydrogen and cells was achieved at 36°C and pH 6.0, the maximal hydrogen evolution rate was found at 41°C and pH 7.0.

Analysis of Compensation Point of Light Using Plane-Type Photosynthetic Bioreactor

Five cylindrical, plane-type, photosynthetic bioreactors of different depths (1, 3, 5, 10, and 20 cm) were used to examine the effect of reactor depth with agitation on hydrogen production using Rhodobacter sphaeroides RV and artificial waste water. This batch test was performed with simulated solar energy using halogen lamps. The irradiation pattern was a sine curve of light12h/dark12h cycle with a peak value of 1 kW/m2. Investigation of the effects of depth showed that the rate of hydrogen production decreased and organic acid concentration increased as reactor depth increased. This was probably due to the increasing effect of the dark zone. Under dark conditions and with strong agitation of the gas/liquid phase in the 1-cm deep reactor, the uptake rate of hydrogen was 100 mL H2/g dry cell weight/day. Hydrogen production and uptake were occurring and balancing in the photosynthetic bioreactor. The light compensation point using a plane-type photosynthetic bioreactor with agitation was about 102 MJ/m3 culture/day. Thus, an important factor to be considered for scaling-up photosynthetic bioreactors is the penetration of light into the cell culture and the absence of a dark zone in the reactor.

Cylindrical-Type Induced and Diffused Photobioreactor

A novel photobioreactor based on a polyacrylate light-receiving face and modified polyester diffusion sheet is presented. With it, the photosynthetic bacterium Rhodobacter sphaeroides RV produced H2 from lactate and glutamate as carbon and nitrogen sources, respectively. The maximum efficiency of energy conversion to H2 was 9.23% using a 1-cm culture width with illumination of 300 W/m2 from a halogen lamp. The reactor showed good proportionality between the rate of gas evolution and incident light energy. A 20-cm deep cylindrical-type photobioreactor that had previously failed to produce H2 was made efficient for H2 production after being modified with induced plates to create a cylindrical induced and diffused photobioreactor (20-cm IDPBR). The productivity of this 20-cm IDPBR was 5.03 mM H2/mM lactate, while that of the unmodified photobioreactor was 1.62 mM H2/mM lactate and that of a 5-cm deep version used as the standard was 3.07 mM H2/mM lactate under light of 300 W/m2. Stirring effects decreased the productivity of the unmodified photobioreactor to 0.20 mM H2/mM lactate. Our novel system could be used to study other light-dependent bioreactions.