Application of photosynthetic microalgae as efficient pH bio-stabilizers and bio-purifiers in sustainable aquaculture of Clarias gariepinus (African catfish) fry

Chlorella lewinii LC172265 and Scenedesmus dimorphus NIES-93 were grown with BG-11 medium and then transferred to fish seedlings' farm and the effects on changes in the pH, nitrite, total ammonia nitrogen and toxic ammonia were studied. Inoculation of the ponds with C. lewinii, S. dimorphus and the combined culture of C. lewinii and S. dimorphus significantly reduced the rise in the pH of the ponds (p<0.05). With these three cultures, the pond pH increased from 6.3±0.03 to only 6.5±0.2, 6.7±0.6 and 6.4±0.1 respectively within a period of 240 hours, as against control pond's pH which increased from 6.3±0.03 to 9.0±0.1 within the same period. Furthermore, inoculation with S. dimorphus reduced the nitrite concentration in the ponds to zero on the 144th hour and the concentration remained zero throughout the experiment. This was closely followed by the combined culture of C. lewinii and S. dimorphus which reduced the nitrite concentration to zero at 240th hour while C. lewinii was the least in nitrite removal. Toxic ammonia was also zeroed by the combined culture of C. lewinii and S. dimorphus at 144th hour of experiment which was followed by C. lewinii (at 192nd hour). Aquaculture ponds co-cultured with microalgae witnessed a maximum fry death rate of 40% which was much lower than 80% death rate observed in the control ponds. These results show that C. lewinii and S. dimorphus are very efficient in sustaining the quality of aquaculture water, and thus prolonging the length of time water can be used before changing.Keywords: nitrogen removal, ammonia, nitrite, fishery, fish pon

Cross-sectional study on COVID-19 prevention and vaccination status of veterinary colleges in Southeast Nigeria

COVID-19 vaccination and compliance with the established prevention protocols are integral to curbing the spread of the COVID-19 virus; however, there is a paucity of information on compliance with these measures among veterinary schools within southeast Nigeria. To fill this gap, we evaluated the vaccination status and individual’s perception of the preventive measures against COVID-19 infections. A cross-sectional study using a self-reported internet-based questionnaire was employed to obtain responses from students and staff of the veterinary colleges in southeast Nigeria. Multivariate binary logistic regression analysis was used to identify significant factors associated with vaccination status and compliance with the COVID-19 prevention protocols by the respondents. A total of 183 individuals participated in the online survey. Although 75% (138/183) of the respondents revealed a willingness to take the COVID-19 vaccine, only 25.1% (46/183) of the respondents had received one or more doses of the COVID-19 vaccine. We observed that male respondents (28 ± 4.4% (95% CI 19–37)) had a higher percentage of vaccinated individuals than female respondents. Furthermore, the academic staff of the veterinary colleges were 39.70 (95% CI 2.50–630.65; ) times more likely to get vaccinated than undergraduate students. The educational status of the respondent greatly contributed to the willingness to get vaccinated, and individuals within the age bracket of 31 to 40 years were 10.2 ± 1.07 (95% CI 1.33–92.25; ) times less likely to comply with the COVID-19 prevention protocols. Although a high proportion of the respondents had a good perception of the COVID-19 prevention protocols, only 25.1% of the members of the veterinary colleges in southeast Nigeria had been vaccinated. Therefore, there is a need to create better awareness channels to improve the vaccination status of members of veterinary colleges in southeast Nigeria

Potentials of microalgae biodiesel production in Nigeria

Bio-energies are renewable, sustainable and environmentally-friendly. Although Nigeria has a lot of various biomass materials, production of bio-fuels in Nigeria is faced with a lot of challenges. It has been argued that large scale production of bio-energies from food crops as replacement or supplements to fossil fuels cannot be realistically achieved because of possible negative effects on food security. There is high potential for largescale production of biodiesel from microalgae in Nigeria. Establishment of biodiesel production industries in Nigeria will have positive effects on socio-economic development of the country. It has been estimated that Nigeria currently needs about 27 thousand barrels of biodiesel per day to be able to replace the entire consumed fossil diesel with B20 blends. There is therefore an urgent need to isolate and develop productive strains that are adapted to non-arable lands in Nigeria, develop appropriate photo bioreactors and culture systems for large scale production of microalgae biodiesel, and develop bioenergy friendly policies and incentives to encourage bio-energy production in Nigeria

Production of Antimicrobial Substances by Lactobacillus plantarum Immobilized in Calcium Alginate Gel Beads

Production of anti-microbial substances by Lactobacillus plantarum, immobilized in calcium alginate gel beads was investigated. The beads were very unstable in De man Rogosa and Sharpe (MRS) medium but the stability of the beads improved by removing potassium and phosphate from the MRS medium. The highest stability of the beads was achieved by addition of calcium chloride to the medium. When 5% calcium chloride was added to the medium, the stability of the beads increased from 24h (when no calcium chloride was added) to 500 h, without adverse effects on the growth and antimicrobial substance production by the immobilized cells. Although the produced antimicrobial substances inhibited the growth of Bacillus cereus, B. subtilis, Listeria monocytogenes, and Escherichia coli, B. subtilis was the most susceptible. Under all the conditions investigated, immobilization of L. plantarum significantly increased the organism’s ability to produce antimicrobial substances. Although suspended cells produced higher antimicrobial substances under anaerobic condition, aerobic condition improved antimicrobial substance production by the immobilized cells. This implies that microaerophilic condition is the best for antimicrobial substance production by L. plantarum.Keywords: Bio-insecticide, anti-microbial substances, Bacillus thuringiensis, endotoxi

Potentials of Exploiting Heterotrophic Metabolism for Biodiesel Oil Production by Microalgae

The current prices of microalgae oils are much higher than oils from higher plants (vegetable oils) mainly due to the high cost of photoautotrophic cultivation of microalgae. However, many strains of microalgae can also grow and produce oil using organic carbons, as the carbon source under dark (heterotrophy) or light conditions (mixotrophy). Lipid productivities of most strains of microalgae are higher in culture systems that incorporate heterotrophic metabolisms (presence of organic carbon source) than under photoautotrophic conditions. This is because for many strains, cell growth rates and final cell concentrations are higher in heterotrophic cultures than in photoautotrophic cultures. Furthermore, in some cases, the oil contents of the cells are also higher in cultures incorporating heterotrophic metabolisms. It has also been reported for some strains that the quality of oil produced in the presence of organic carbon sources are more suitable for biodiesel oil production than those produced under photoautotrophic conditions. Thus, heterotrophy can be used to reduce the cost of biodiesel oil production, but the effectiveness of the various organic carbons in supporting cell growth and oil accumulation depends on the strain and other culture conditions. Use of wastewaters for cultivation of microalgae can further substantially reduce the cost of production (since they contain carbon, nitrogen, and other nutrients) and also reduce the requirement for freshwater. Generally, many factors such as nitrogen limitation, phosphate limitation, silicon limitation, control of pH, and low temperature can be used to increase oil accumulation, although their effectiveness depends on the strain and other culture conditions

Effects of light intensity and photoperiod on growth, lipid accumulation and fatty acid composition of Desmodesmus subspicatus LC172266 under photoautotrophic cultivation

Microalgae oil accumulation in their natural growing states hardly reaches the quantities needed to replace fossil-derived diesel. Therefore, for algae to be used as biofuel feedstock, their growths are manipulated with the aim of achieving high cell density and high lipid accumulation. Two major factors affecting microalgal biomass and lipid productivity are light intensity and photoperiod. In the present study, Desmodesmus subspicatus was grown photoautotrophically under varying light intensities and photoperiods with a view to assessing the growth, lipid accumulation potential and fatty acid composition. Whereas the optimal light intensity for biomass production of the microalga was 5000 lx, that for lipid productivity was 3500 lx. At 5000 lx and 18: 6 h light/dark cycle, biomass yield, lipid content and lipid productivity were highest, at values of 1.92 ± 0.03 g/L, 53% and 118.80 ± 2.04 mgL-1day -1 respectively. The major fatty acid of the alga was oleic acid irrespective of light changes. The quantities of lipid accumulated and the properties of the fatty acid methyl esters showed that Desmodesmus subspicatus LC172266 is an ideal feedstock for biodiesel production

Potentials of exploiting heterotrophic metabolism for biodiesel oil production by microalgae.

The current prices of microalgae oils are much higher than oils from higher plants (vegetable oils) mainly due to the high cost of photoautotrophic cultivation of microalgae. However, many strains of microalgae can also grow and produce oil using organic carbons, as the carbon source under dark (heterotrophy) or light conditions (mixotrophy). Lipid productivities of most strains of microalgae are higher in culture systems that incorporate heterotrophic metabolisms (presence of organic carbon source) than under photoautotrophic conditions. This is because for many strains, cell growth rates and final cell concentrations are higher in heterotrophic cultures than in photoautotrophic cultures. Furthermore, in some cases, the oil contents of the cells are also higher in cultures incorporating heterotrophic metabolisms. It has also been reported for some strains that the quality of oil produced in the presence of organic carbon sources are more suitable for biodiesel oil production than those produced under photoautotrophic conditions. Thus, heterotrophy can be used to reduce the cost of biodiesel oil production, but the effectiveness of the various organic carbons in supporting cell growth and oil accumulation depends on the strain and other culture conditions. Use of wastewaters for cultivation of microalgae can further substantially reduce the cost of production (since they contain carbon, nitrogen, and other nutrients) and also reduce the requirement for freshwater. Generally, many factors such as nitrogen limitation, phosphate limitation, silicon limitation, control of pH, and low temperature can be used to increase oil accumulation, although their effectiveness depends on the strain and other culture conditions