宮永 一彦

In a fluidized-bed porous carrier system, organic carbon and nitrogen in wastewater can be removed simultaneously. However, the excess sludge generated in the system has not been focused on. On the other hand, a membrane system can separate suspended solid from treated water and retain slowly growing microbes such as nitrifiers in the aeration tank. Porous carrier and membrane hybrid system with these respective advantages has been studied to enhance the nitrogen removal efficiency. In this study, the hybrid system was investigated to compare with a conventional carrier system in terms of the nitrogen removal rate from complex artificial wastewater (CAW) containing polypeptone as a nitrogen source. Moreover, the amounts of excess sludge generated in both systems were evaluated. Longer sludge retention time of the hybrid system was expected to enhance the microbial autolysis and lead to the reduction of the excess sludge. Consequently, the amount of excess sludge generated in the hybrid system was reduced to about one-fourth of that in the carrier system for about two months. In addition, a lot of slowly growing protozoa preyed on the microorganisms, which might have contributed to the reduction of excess sludge. The removal rates of organic carbon and nitrogen in the hybrid system were higher than in the carrier system, due to the highly concentrated microorganisms in the hybrid system. A batch operation revealed that the nitrogenous compounds of polypeptone in CAW were rapidly removed by assimilation, while urea in the artificial wastewater was mainly removed by nitrification. Consequently, total nitrogen concentration in CAW containing polypeptone decreased faster than in artificial wastewater containing urea. These results show that nitrogenous compounds in CAW are easy to be removed. The hybrid system is an efficient system to enhance the nitrogen removal and has a capability to reduce the excess sludge.

In a fluidized-bed porous carrier system, organic carbon and nitrogen in wastewater can be removed simultaneously. However, the excess sludge generated in the system has not been focused on. On the other hand, a membrane system can separate suspended solid from treated water and retain slowly growing microbes such as nitrifiers in the aeration tank. Porous carrier and membrane hybrid system with these respective advantages has been studied to enhance the nitrogen removal efficiency. In this study, the hybrid system was investigated to compare with a conventional carrier system in terms of the nitrogen removal rate from complex artificial wastewater (CAW) containing polypeptone as a nitrogen source. Moreover, the amounts of excess sludge generated in both systems were evaluated. Longer sludge retention time of the hybrid system was expected to enhance the microbial autolysis and lead to the reduction of the excess sludge. Consequently, the amount of excess sludge generated in the hybrid system was reduced to about one-fourth of that in the carrier system for about two months. In addition, a lot of slowly growing protozoa preyed on the microorganisms, which might have contributed to the reduction of excess sludge. The removal rates of organic carbon and nitrogen in the hybrid system were higher than in the carrier system, due to the highly concentrated microorganisms in the hybrid system. A batch operation revealed that the nitrogenous compounds of polypeptone in CAW were rapidly removed by assimilation, while urea in the artificial wastewater was mainly removed by nitrification. Consequently, total nitrogen concentration in CAW containing polypeptone decreased faster than in artificial wastewater containing urea. These results show that nitrogenous compounds in CAW are easy to be removed. The hybrid system is an efficient system to enhance the nitrogen removal and has a capability to reduce the excess sludge.

For the development of a sewer pipe that removes dissolved organic carbon (DOC) and nitrogen, a rectangular channel with a fabricated porous ceramic bed was investigated. The experimental channel was 1 m long, 2.0 × 10-2 m wide, and 2.5 × 10-2 m deep, the total volume being 0.811. Blocks of the ceramic bed with 2.0 × 10-2 m2 total surface area and 5.0 × 10-3 m thickness were installed along the channel bed for the immobilization of microorganisms. Synthetic wastewater was used as the model sewage. Removal of organic carbon and nitrogen was carried out with or without aeration. Dissolved oxygen (DO) and pH microelectrodes were employed to analyze structure of the biofilm, which played an important role in the removal of both organic carbon and nitrogen. The results give evidence that the combination of aeration and biofilm development enhanced the simultaneous removal of organic carbon and nitrogen. Microelectrode study revealed that the biofilm was rough and heterogeneous in both vertical and horizontal directions and had an average thickness of 2.5-5 mm. The biofilm, consisting of an aerobic/anaerobic layer, was suggested to be responsible for the nitrification/denitrification process, while the aeration accelerated the removal of total organic carbon (TOC), NH4 or NO2 from the model sewage. Sequential nitrification/denitrification proceeded in the biofilm even when aeration was carried out. This study suggests that the immobilization of microbes inside the sewer pipe may be effective for the simultaneous removal of organic carbon and nitrogen in the sewage line. © 2002 Elsevier Science B.V. All rights reserved.

For the development of a sewer pipe that removes dissolved organic carbon (DOC) and nitrogen, a rectangular channel with a fabricated porous ceramic bed was investigated. The experimental channel was 1 m long, 2.0 x 10(-2) m wide, and 2.5 x 10(-2) m deep, the total volume being 0.811. Blocks of the ceramic bed with 2.0 x 10(-2) m(2) total surface area and 5.0 x 10(-3) m thickness were installed along the channel bed for the immobilization of microorganisms. Synthetic wastewater was used as the model sewage. Removal of organic carbon and nitrogen was carried out with or without aeration. Dissolved oxygen (DO) and pH microelectrodes were employed to analyze structure of the biofilm, which played an important role in the removal of both organic carbon and nitrogen. The results give evidence that the combination of aeration and biofilm development enhanced the simultaneous removal of organic carbon and nitrogen. Microelectrode study revealed that the biofilm was rough and heterogeneous in both vertical and horizontal directions and had an average thickness of 2.5-5 mm. The biofilm, consisting of an aerobic/anaerobic layer, was suggested to be responsible for the nitrification/denitrification process, while the aeration accelerated the removal of total organic carbon (TOC), NH4 or NO2 from the model sewage. Sequential nitrification/denitrification proceeded in the biofilm even when aeration was carried out. This study suggests that the immobilization of microbes inside the sewer pipe may be effective for the simultaneous removal of organic carbon and nitrogen in the sewage line. (C) 2002 Elsevier Science B.V All rights reserved.

Porous carriers in fluidized bed have been used for microbial immobilization in order to simultaneously remove organic carbon and nitrogen in wastewater. In particular, multifunctional microbial reactions in the carrier, such as simultaneous nitrification/denitrification, play important roles in nitrogen removal. To enhance these reactions the substrates should be supplied into the carrier with appropriate rates. This is because the denitrification reaction was often limited by the supply of organic substances, due to overgrowth of heterotrophs in the region near the carrier surface. A porous carrier-membrane hybrid process was found to have improved nitrogen removal efficiency, due to stimulated denitrification as well as nitrification. The hybrid system achieved a 30% higher nitrogen removal ratio than that in the fluidized porous carrier system. Microelectrode studies revealed that although intracarrier denitrification rate in a conventional fluidized bed was limited by organic carbon, this limitation was reduced in the hybrid process, resulting in the increased intracarrier denitrification rate. These effects were due to suppressed glucose oxidation in aerobic region in the hybrid process. (C) 2002 Elsevier Science B.V. All rights reserved.

Callus induced from the leaves of Eucommia ulmoides, a medicinal woody plant, was cultivated to produce a factor capable of enhancing collagen synthesis in animal cells (FECS). However, the callus was too rigid to be divided into small pieces by a hydrodynamic force during the cultivation, which led to a slow callus growth characterized by enlargement of the callus size rather than increase in the callus number. Improved growth rate of the callus with smaller sizes and cavity formation in the central region of the callus with its enlargement, implied the occurrence of transfer limitation of nutrient(s) inside the callus. Distributions of the principal nutrients of sugar, nitrogen and dissolved oxygen concentrations across the cultivated callus were simulated by a kinetic model consisting of nutrients diffusion and bioreaction kinetics, suggesting that oxygen transfer in the callus was the Limiting factor for the callus growth. A callus growth model considering the effect of the nutrients' transfer and cell death kinetics in the callus which was caused by the oxygen depletion successfully described the callus enlargement process. Based on these results, a newly developed bioreactor with a fragmentation device enabled the callus to grow with enhanced growth rate by controlling the callus at small sizes during the cultivation. (C) 2001 IMACS. Published by Elsevier Science B.V. All rights reserved.

A suspension culture of tobacco cells was transformed with a gene encoding barley lectin to obtain an efficient production system of lectin. Lectin excreting transgenic tobacco was constructed by transformation with barley lectin deleted of the C- terminal vacuole targeting peptide (CTPP). 2,4Dichlorophenoxyacetic acid (2,4- D) was examined for its effect on the excretion of lectin at different concentrations from 0 to 5 mg 1 2,4- D addition increased excretion efficiency, defined as the amount of excreted lectin per cell, but reduced the growth rate. Microscopic observations showed loosening of the cell wall, which is assumed to be one of the causes of the enhanced excretion. Decrease in extracellular lectin was observed in spite of the growth of cells, which was confirmed to be caused by a degradation process in the culture medium. These results suggest that an efficient production process of lectin would include a process of simultaneously removing culture medium with high lectin content before degradation occurs and maintaining the cells at high excretion efficiency.

Cultured plant cells are often highly heterogeneous in terms of secondary metabolite production. We have developed a quantitative determination method that uses an image processing system to estimate such individual cell characteristics as content of the secondary metabolite, anthocyanin. In this study, strawberry cells producing anthocyanins were grown in modified Linsmaier-Skoog medium. Anthocyanin accumulation profiles of individual cells depended on medium compositions and were quantitatively determined using the new method. The modified medium supplemented with riboflavin and high sugar concentration showed a markedly higher anthocyanin accumulation profile and pigmented cell ratio than the other modified media. The maximum content was about 11 mg (g-fresh cell weight)(-1) which was three times higher than that in the control medium. Moreover, the anthocyanin accumulation profiles in the individual cells cultured in all modified media could be approximated to the parts of the normal distribution curves with the constant variance. (C) 2000 Elsevier Science S.A. All rights reserved.

Anthocyanin accumulation in strawberry (Fragaria ananassa) cells cultured on a solid medium was monitored using an image-processing system that did not require direct sampling or destruction of the cells. Because of the intercellular heterogeneity of secondary metabolite production in plant cell cultures, the maximum metabolite concentration in individual cells is often more than 10 times higher than that of the average concentration. An image-processing based method enabled the growth and the pigmentation behavior of individual cells to be traced. Changes in the time courses of the anthocyanin content of individual cells differed from each other, although the average anthocyanin contents increased gradually with time in a batch culture. However, these various changing patterns in the anthocyanin content of each cell were independent of the cell cycle. In addition, image analysis revealed that the two cells just after cell division were almost identical to each other both in size and anthocyanin content. The proposed method which uses an image-processing system provides a useful tool for analyzing the secondary metabolism in individual cultured plant cells.

Plant-cultured cells are often highly heterogeneous in secondary metabolite productivity. The industrial application for large-scale metabolite production requires establishment of a stable high-producing cell line. In this study, image analysis of the individual cell is investigated as a method for evaluation of a heterogeneous cell population, and compared with the conventional method of estimation, which is based on average-cell productivity. Among strawberry cells producing anthocyanins, cells with a wide-range of pigment concentration were observed and maximum anthocyanin content was 10 times higher than the average value. In addition, a change of the frequency distribution was revealed in batch cultivation. (C) 2000 John Wiley & Sons, Inc.

現在の塩化ビニルモノマー(VCM)製造工程においては様々な含塩素有機化合物が副生し、燃焼あるいは活性汚泥などによって処理されている。プロセス内ゼロエミッションのためにば副生成物の分離や物質変換に関わる新たな要素技術の開発が求められる。微生物反応を利用する塩素化エチレンの嫌気的脱塩素化は、生成物をポリ塩化ビニル(PVC)製造の原料として再利用できることが期待できる。製品寿命を終えたPVCの多くは燃焼か埋め立て処分される。PVCの選択的脱塩素化で塩化水素に変換できれば、塩化第二鉄やポリ塩化アルミニウムの原料として利用できる。このような異種プロセス間への新たな物質フローを構築すれば塩化ナトリウムの電気分解に始まり、製品寿命を終えると再び塩化ナトリウムに戻る一連の塩素フローの中で、製品要素としての塩素の寿命を長く設定することができ、新たな電気分解による塩素の製造量を減らすことにつながる。 一方、塩化ナトリウムの電気分解で生成する塩素を利用するためには、バランス産業と呼ばれるように同時に生成するカセイソーダ、水素ガスの生成量に見合う利用プロセスを構築するのが理想的である。しかし日本においてはPVC製造のために必要な塩素のバランスをとることはできず、含塩素半製品輸入によって調整している。種々の添加物を必要とする軟質塩化ビニルを非塩素系の材料に転換することは技術的に可能である。この転換によって、現在の塩素需要過剰状態は解消され、バランス型にすることができる。これを可能にするためには、経済的に可能な種々の技術開発が求められる。

Fragaria ananassa (strawberry) callus, which produced high amounts of anthocyanin in the dark, was isolated from a cell line not producing anthocyanin. The isolated callus (FAR) was homogeneous and more than 90% of the cells were pigmented. The FAR callus accumulated more than 1000 mu g of anthocyanin per g fresh cell in the dark. Four different basal solid media were examined to maintain FAR callus: Though growth rate and anthocyanin concentration were different on each media, total anthocyanin production was about the same at 400 mu g anthocyanin/0.1 g fresh cell wt after 22 days. This FAR cell line could therefore be used for the industrial production of anthocyanin.