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James C. Ogbonna

Bio: James C. Ogbonna is an academic researcher from University of Nigeria, Nsukka. The author has contributed to research in topics: Photobioreactor & Fermentation. The author has an hindex of 31, co-authored 106 publications receiving 3229 citations. Previous affiliations of James C. Ogbonna include Hamburg University of Technology & Godfrey Okoye University.


Papers
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Journal ArticleDOI
TL;DR: The problem of light supply to photobioreactors can be solved by developing photosynthetic cellcultivation systems where light is either substituted or supplemented, and cyclicphotoautotrophic/heterotrophic cultivation system can be used to achieve continuous cell growth under day/night cycles.
Abstract: Although the potential of photosyntheticmicroorganisms for production of various metabolitesand in environmental bioremediation is recognized,their practical application has been limited by thedifficulty in supplying light efficiently tophotobioreactors. Various types of photobioreactorwith high illumination to volume ratios have beenproposed, but most are limited by cost, mass transfer,contamination, scale-up or a combination of these.The problem of light supply to photobioreactorscan be solved by developing photosynthetic cellcultivation systems where light is either substitutedor supplemented. Many strains of photosynthetic cellsare capable of heterotrophic growth under darkconditions and their heterotrophic culture can be usedfor efficient production of biomass and somemetabolites. However, light is absolutely required forefficient production of some metabolites. In suchcases, there is a need to supplement the heterotrophicwith photoautotrophic metabolism. Inphotoheterotrophic (mixotrophic) culture, thephotoautotrophic and heterotrophic metabolisms can beexploited for efficient production of usefulmetabolites but it has many problems such as processoptimization in terms of making a balance between thephotoautotrophic and heterotrophic metabolism. Another promising system is the sequentialheterotrophic/ photoautotrophic cultivation system,where the cells are cultivated heterotrophically tohigh concentrations and then passed through aphotobioreactor for accumulation of the desiredmetabolite(s). Furthermore, cyclicphotoautotrophic/heterotrophic cultivation system canbe used to achieve continuous cell growth underday/night cycles. This involves cultivating thecells photoautotrophically using solar light duringthe day and then adding controlled amount of organiccarbon source during the night for heterotrophicgrowth. In this review, these various systems arediscussed with some specific examples.

201 citations

Journal ArticleDOI
TL;DR: Both in terms of economy and efficiency,aerobic dark conditions were the best for wastewatertreatment using R. sphaeroides and C.sorokiniana, but light was necessary with S.platensis.
Abstract: The growth characteristics and nutrient removal fromsynthetic wastewater by Rhodobacter sphaeroides,Chlorella sorokiniana and Spirulinaplatensis were investigated under aerobic dark(heterotrophic) and aerobic light (photoheterotrophic)conditions. Both in terms of economy and efficiency,aerobic dark conditions were the best for wastewatertreatment using R. sphaeroides and C.sorokiniana, but light was necessary with S.platensis. Neither growth nor nutrient removalcharacteristics of the cells were affected insynthetic wastewater with as high as 10 000 ppmacetate, 1000 ppm propionate, 700 ppm nitrate and 100 ppmphosphate. Although R. sphaeroides and C. sorokiniana showed good growth in syntheticwastewater containing 400 ppm of ammonia, S.platensis was completely inhibited.When grown as a monoculture, none of thestrains could simultaneously remove acetate,propionate, ammonia, nitrate and phosphate from thewastewater. R. sphaeroides could remove allthe above nutrients except nitrate, but the rate of removal was relatively low. The rate of nutrientsremoval by C. sorokiniana was higher, but theorganism could not remove propionate; S.platensis could efficiently remove nitrate, ammoniaand phosphate, but none of the organic acids. A mixedculture of R. sphaeroides and C.sorokiniana was therefore used for simultaneousremoval of organic acids, nitrate, ammonia andphosphate. The optimum ratio of the cells depended onthe composition of the wastewater.

184 citations

Journal ArticleDOI
TL;DR: The effectiveness of the static mixers was higher at higher standing biomass concentrations and on cloudy days (solar radiation below 6 MJ m–2 day–1) and in outdoor culture of Chlorella sorokiniana, the photobioreactor withstatic mixers gave higher biomass productivities irrespective of the standing biomass concentration and solar radiation.
Abstract: The feasibility of improving mass transfer characteristics of inclined tubular photobioreactors by installation of static mixers was investigated. The mass transfer characteristics of the tubular photobioreactor varied depending on the type (shape) and the number of static mixers. The volumetric oxygen transfer coefficient (k La) and gas hold up of the photobioreactor with internal static mixers were significantly higher than those of the photobioreactor without static mixers. The k La and gas hold up increased with the number of static mixers but the mixing time became longer due to restricted liquid flow through the static mixers. By installing the static mixers, the liquid flow changed from plug flow to turbulent mixing so that cells were moved between the surface and bottom of the photobioreactor. In outdoor culture of Chlorella sorokiniana, the photobioreactor with static mixers gave higher biomass productivities irrespective of the standing biomass concentration and solar radiation. The effectiveness of the static mixers (average percentage increase in the productivities of the photobioreactor with static mixers over the productivities obtained without static mixers) was higher at higher standing biomass concentrations and on cloudy days (solar radiation below 6 MJ m–2 day–1).

174 citations

Journal ArticleDOI
TL;DR: Production of astaxanthin by sequential heterotrophic-photoautotrophiccultivation of a green alga, Haematococcus pluvialis was investigated and the results are very high compared to the data in the literature.
Abstract: Production of astaxanthin by sequential heterotrophic-photoautotrophiccultivation of a green alga, Haematococcus pluvialis was investigated.This involved cultivating the cells heterotrophically to high cellconcentration, followed by illumination of the culture for astaxanthinaccumulation. The optimum pH and temperature for heterotrophic biomassproduction were 8 and 25 °C, respectively. There was no significantdifference in the specific growth rate of the cells when acetateconcentration was varied between 10 mM and 30 mM. However, cellgrowth was inhibited at higher acetate concentrations. A pH stat methodwas then used for fed-batch heterotrophic culture, using acetate as theorganic carbon source. A cell concentration of 7 g L-1 wasobtained. Higher cell concentration could not be obtained because the cellschanged from vegetative to cyst forms during the heterotrophic cultivation.However, by using repeated fed-batch processes, the cells could bemaintained in the vegetative form, leading to more than two times increasein cell number output rate. When the vegetative cells were transferred tophotoautotrophic phase, there was a sharp decrease in the cell number andonly very few cells encysted and accumulated astaxanthin. On the otherhand, when the shift from heterotrophic to photoautotrophic condition wasdone when most of the cells had encysted, there was still a decrease in cellnumber but astaxanthin accumulation was very high. The astaxanthinconcentration (114 mg L-1) and productivity (4.4 mg L-1d-1) obtained by this sequential heterotrophic-photoautotrophiccultivation method are very high compared to the data in the literature.

165 citations

Journal ArticleDOI
TL;DR: An internally illuminated stirred tank photobioreactor is designed and constructed that can easily be scaled up while maintaining the light supply coefficient and thus the productivity constant and is coupled with an artificial light source coupled with the solar light collecting device.

165 citations


Cited by
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Journal Article
Fumio Tajima1
30 Oct 1989-Genomics
TL;DR: It is suggested that the natural selection against large insertion/deletion is so weak that a large amount of variation is maintained in a population.

11,521 citations

Journal ArticleDOI
TL;DR: In this article, the authors reviewed the technologies underpinning microalgae-to-bio-fuels systems, focusing on the biomass production, harvesting, conversion technologies, and the extraction of useful co-products.
Abstract: Sustainability is a key principle in natural resource management, and it involves operational efficiency, minimisation of environmental impact and socio-economic considerations; all of which are interdependent. It has become increasingly obvious that continued reliance on fossil fuel energy resources is unsustainable, owing to both depleting world reserves and the green house gas emissions associated with their use. Therefore, there are vigorous research initiatives aimed at developing alternative renewable and potentially carbon neutral solid, liquid and gaseous biofuels as alternative energy resources. However, alternate energy resources akin to first generation biofuels derived from terrestrial crops such as sugarcane, sugar beet, maize and rapeseed place an enormous strain on world food markets, contribute to water shortages and precipitate the destruction of the world's forests. Second generation biofuels derived from lignocellulosic agriculture and forest residues and from non-food crop feedstocks address some of the above problems; however there is concern over competing land use or required land use changes. Therefore, based on current knowledge and technology projections, third generation biofuels specifically derived from microalgae are considered to be a technically viable alternative energy resource that is devoid of the major drawbacks associated with first and second generation biofuels. Microalgae are photosynthetic microorganisms with simple growing requirements (light, sugars, CO 2 , N, P, and K) that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and valuable co-products. This study reviewed the technologies underpinning microalgae-to-biofuels systems, focusing on the biomass production, harvesting, conversion technologies, and the extraction of useful co-products. It also reviewed the synergistic coupling of microalgae propagation with carbon sequestration and wastewater treatment potential for mitigation of environmental impacts associated with energy conversion and utilisation. It was found that, whereas there are outstanding issues related to photosynthetic efficiencies and biomass output, microalgae-derived biofuels could progressively substitute a significant proportion of the fossil fuels required to meet the growing energy demand.

4,432 citations

Journal ArticleDOI
TL;DR: A forum to review, analyze and stimulate the development, testing and implementation of mitigation and adaptation strategies at regional, national and global scales as mentioned in this paper, which contributes to real-time policy analysis and development as national and international policies and agreements are discussed.
Abstract: ▶ Addresses a wide range of timely environment, economic and energy topics ▶ A forum to review, analyze and stimulate the development, testing and implementation of mitigation and adaptation strategies at regional, national and global scales ▶ Contributes to real-time policy analysis and development as national and international policies and agreements are discussed and promulgated ▶ 94% of authors who answered a survey reported that they would definitely publish or probably publish in the journal again

2,587 citations

Book ChapterDOI
01 Jan 1982
TL;DR: In this article, the authors discuss leading problems linked to energy that the world is now confronting and propose some ideas concerning possible solutions, and conclude that it is necessary to pursue actively the development of coal, natural gas, and nuclear power.
Abstract: This chapter discusses leading problems linked to energy that the world is now confronting and to propose some ideas concerning possible solutions. Oil deserves special attention among all energy sources. Since the beginning of 1981, it has merely been continuing and enhancing the downward movement in consumption and prices caused by excessive rises, especially for light crudes such as those from Africa, and the slowing down of worldwide economic growth. Densely-populated oil-producing countries need to produce to live, to pay for their food and their equipment. If the economic growth of the industrialized countries were to be 4%, even if investment in the rational use of energy were pushed to the limit and the development of nonpetroleum energy sources were also pursued actively, it would be extremely difficult to prevent a sharp rise in prices. It is evident that it is absolutely necessary to pursue actively the development of coal, natural gas, and nuclear power if a physical shortage of energy is not to block economic growth.

2,283 citations