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Biodiesel production waste cooking oil is usually limited by its high free fatty acid and moisture content. The synergetic effect of both base and acid source from biomass was employed to proffer way out to this challenge. This study shows the coupled development of sulfonated carbonized corn cob (S-CCC) and calcined cow-bone (C-CB) catalysts for transesterification of waste cooking oil. The catalyst was prepared by physically mixing several mass percentages of S-CCC and C-CB (fluorapatite) in strategic proportions. The maximum biodiesel yield of 96.2 % was attained for catalyst mixture of 60 wt% and 40 wt%. The developed catalyst mixture was characterized by Fourier Transform Infrared Ray (FTIR), powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Brunauer–Emmett-Teller (BET). The surface area (472.3 m2/g), pore size (2.4330 nm) and volume (0.1380 cc/g) were obtained for the catalyst. The XRD shows that the crystallized structure of the bifunctional catalyst was formed majorly between 2 theta 10 and 65.Also the SEM shows a well dispersive pattern of the particles of the catalyst. The developed catalyst was employed for biodiesel optimization studies by varying factors such as time, temperature, catalyst loading and methanol: oil using optimal design under the response surface methodology. Maximum yield of 98.98 % was attained at time 6 h, temperature 65 °C, catalyst loading 6 %wt/ wt of oil and methanol to oil ratio of 11.75:1. It was observed that time and temperature had notable effect on the biodiesel yield.

The performance of a hybrid of Saccharomyces cerevisiae and Saccharomyces paradoxus (Yeast B) compared with an industrial strain of S. cerevisiae (Yeast A) was studied. The two strains of yeasts: Yeast A obtained from the Bioresources Development Centre, National Biotechnology Development Agency Ogbomosho and Yeast B obtained from Scotch Whisky Research Laboratory in Edinburgh, Scotland (Strain 63M) were studied using the SLSF method for bioethanol production at various initial starch concentrations (20, 30 and 50%). The cassava starch used was extracted from Tropical Manihot esculenta (TME 419) cassava strain while the SLSF method for bioethanol production was initiated by adding granular starch hydrolysing enzyme with the yeast strains into the starch solutions at room temperature. The results obtained showed that Yeast B has higher bioethanol yield and tolerance generating 70.34, 87.34 and 120.53 ml/L compared to the Yeast A which produced 63.4, 72.73 and 112.6 ml/L at 20, 30 and 50% starch concentrations respectively. The study suggests that the hybrid strain of S. cerevisiae and S. paradoxus out performs the industrial strain and can favorably substitute or displace the industrial strains for bioethanol production. Key words: Bioethanol, cassava, fermentation, hybrid, simultaneous liquefaction saccharification and fermentation (SLSF), yeast, Saccharomyces cerevisiae, Saccharomyces paradoxus.

Vinasse is a highly polluting by-product waste from bioethanol production processes. In this work, the biochemical methane potential (BMP), biodegradability index (BI), competitiveness index (CI) and physicochemical properties of cassava vinasse (CV) obtained from an ethanol distillery were studied to gain a better understanding of its characteristics and suggest alternative treatment routes and usage. At 28 o C, the CV used had a moisture content, specific gravity, refractive index and Brix value of 93%, 1.03, 1.34 and 5.88% sucrose, respectively. It exhibited relatively high Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) of 62000-736500 and 21620-25000 mg/L, respectively. These, coupled with its acidic pH of 4.2–4.8 and cyanuric acid content of 386–450 mg/L, emphasized its potential as a pollutant both on land and water. The high volatile solids content of 71580-72250 mg/L and BOD-to-COD ratio of 0.3:1–0.4:1 both point to the presence of biodegradable organic matter. The CV contained macro and micro-nutrients in addition to salts of phosphates, nitrates and sulphates. At standard temperature and pressure, a BMP of 247.10 NmL/gVS points to the potential of the CV as a bioenergy resource. Also, while a BI of 0.82 indicated that 82% of organic matter in CV is degradable, a CI above 10 means no competition between the methanogens and the sulphate-reducing bacteria (SRB) if the CV is subjected to anaerobic digestion (AD). Based on these results, the CV could be treated via AD with simultaneous biogas production and, to some extent, used as a nutrient source for microbial-driven bioprocesses.

This study focused on the effect of bio-digester shape on biogas production. Bio-digesters of 15-dm3 each with different shapes (cylindrical, cubical and conical) were constructed and their performances for biogas production were investigated using poultry droppings. Also, the performance of the best bio-digester was further assessed using poultry droppings, cow dung and piggery waste. Additionally, the biogas production process was modeled and optimized by co-digesting plantain peels with the animal wastes using the best bio-digester. The average daily biogas productions for cylindrical, cubical and conical-shaped bio-digesters were 0.58, 0.46 and 0.36 dm3/day, respectively. Using 2.5-dm3 cylindrical-shaped bio-digesters, daily average biogas productions for cow dung, poultry droppings and piggery waste were 0.40, 0.23 and 0.01 dm3/day, respectively. Using the developed model coupled with genetic algorithm, the optimum biogas production was 13.65 dm3 with substrate combination of 0.7 kg of poultry droppings, 0.0004 kg of cow dung, 0.6 kg of piggery waste and 0.2 kg of plantain peels. The results showed cylindrical-shaped bio-digester was the best for biogas production, while cow dung gave the highest biogas production. The study demonstrated that maximum biogas production could be obtained using combination of animal wastes supplemented with plantain peels.

The quality of life on earth is directly linked to the overall quality of the environment. The natural ecosystem encompasses all living and non-living things existing on earth naturally. It is an environment that interacts with all living species, but which may be contaminated with diesel a derivative of hydrocarbons. Diesel spills contaminate both aquatic and terrestrial environments. To prevent the environmental and health risks of this, remediation needs to be advanced. Bioremediation, degradation by microbes, is one of the suitable methods for cleaning diesel contamination. In the present work, the biodegradation of diesel oil contaminated soil has been investigated comparatively with Pseudomonas aeruginosa and Pseudomonas fluorescence coupled with fertilizer as essential nutrients. Based on observations carried out in 18 days, Pseudomonas aeruginosa alone as well as in the presence of essential inorganic nutrients was found to exhibit higher remediation potential in degrading soil contaminated with diesel oil than Pseudomonas fluorescence.

In this study, comparative potential effects of commercial activated carbon (CAC) and plantain peel-derived biochar (PPBC) of different particle sizes and dosage to stimulate petroleum hydrocarbon biodegradation in soil were investigated. Microcosms containing soil were spiked with weathered Bonny light crude oil (WBLCO) (10% w/w) and amended with different particle sizes (0.02, 0.07 and 0.48 mm) and dosage (20, 30 and 40 g) of CAC and PPBC, respectively. The bioremediation experiments were carried out for a period of 28 days under laboratory conditions. The results showed that there was a positive relationship between the rate of petroleum hydrocarbons reduction and presence of the CAC and PPBC in crude oil contaminated soil microcosms. The WBLCO biodegradation data fitted well to the first-order kinetic model. The model revealed that WBLCO contaminated-soil microcosms amended with CAC and PPBC had higher biodegradation rate constants (k) as well as lower half-life times (t1/2) than unamended soil (natural attenuation) remediation system. The rate constants increased while half-life times decreased with decreased particle size and increased dosage of amendment agents. ANOVA statistical analysis revealed that WBLCO biodegradation in soil was significantly (p = 0.05) influenced by the addition of CAC and biochar amendment agents, respectively. However, Tukey’s post hoc test (at p = 0.05) showed that there was no significant difference in the bioremediation efficiency of CAC and PPBC. Thus, amendment of soils with biochar has the potential to be an inexpensive, efficient, environmentally friendly and relatively novel strategy to mitigate organic compound-contaminated soil.

The focus of the review paper is to discuss how biotechnological innovations are opening new frontiers to mitigate nutrition in key agricultural crops with potential for large-scale health impact to people in Africa. The general objective of the Africa Biofortified Sorghum (ABS) project is to develop and deploy sorghum with enhanced pro-vitamin A to farmers and end-users in Africa to alleviate vitamin A-related micronutrient deficiency diseases. To achieve this objective the project technology development team has developed several promising high pro-vitamin A sorghum events. ABS 203 events are so far the most advanced and well-characterised lead events with about 12 μg β-carotene/g tissue which would supply about 40–50 % of the daily recommended vitamin A at harvest. Through gene expression optimisation other events with higher amounts of pro-vitamin A, including ABS 214, ABS 235, ABS 239 with 25, 30–40, 40–50 μg β-carotene/g tissue, respectively, have been developed. ABS 239 would provide twice recommended pro-vitamin A at harvest, 50–90 % after 3 months storage and 13–45 % after 6 months storage for children. Preliminary results of introgression of ABS pro-vitamin A traits into local sorghum varieties in target countries Nigeria and Kenya show stable introgression of ABS vitamin A into local farmer-preferred sorghums varieties. ABS gene Intellectual Property Rights and Freedom to Operate have been donated for use royalty free for Africa. Prior to the focus on the current target countries, the project was implemented by fourteen institutions in Africa and the USA. For the next 5 years, the project will complete ABS product development, complete regulatory science data package and apply for product deregulation in target African countries.

This study aimed at using a non-edible NO (neem oil) for biodiesel production by modeling and optimizing the two-step process involved. A significant quadratic regression model (p

We assessed the perception of farmers towards potential adoption of genetic modification (GM) technology for improving health, food security and agricultural productivity using a semi-structured interview. A total sample of 54 small-scale farmers participated in 6 focus group meetings (FGMs) and 23 in-depth interviews at six locations in Ghana and Nigeria (West Africa). Our results reveal that most farmers have a very poor understanding of GM technology which they often misunderstood as traditional plant breeding biotechnology. While most respondents focused on the potential benefits of GM technology including high-yielding varieties, better nutritional value and shorter growing cycle crop traits, only a few respondents were concerned about the potential health and environmental risks of GM technology. Root and tuber crops such as cassava, yam and sweet potato were mostly discussed for health improvement and food security through GM technology. This study emphasizes the need to recognize challenges such as lack of awareness, inadequate training, low level of education and poor extension services among others in introducing new technology including GM technology to resource poor farmers in African countries like Ghana and Nigeria. We conclude that failure to address these challenges will impede the adoption of GM technology. Therefore, Ghanaian and Nigerian government(s) must put in place policy measures to address these problems. Keywords: Food security, health improvement, genetic modification (GM) technology, Ghana, Nigeria, West Africa farmers African Journal of Biotechnology , Vol. 13(2), pp. 245-256, 8 January, 2014

Tannery wastewater treatment using two isolated micro-organisms (Bacillus subtilis and Pseudomonas fragii) has been investigated in the present study. The growth patterns, pH normalisation and the abilities of these micro-organisms to reduce the concentrations of chemical oxygen demand (COD), total suspended solids (TSS) and chloride were studied using the shake flask apparatus. The specific growth rate and biomass concentration of B. subtilis and P. fragii were observed 0.138 h−1 and 3.01 mg/l and 0.051 h−1 and 2.34 mg/l, respectively, after 84 h. Both micro-organisms normalised pH of the wastewater. COD removal efficiency for B. subtilis was 87.6% while that of P. fragii was 85.2%. For TSS, B. subtilis caused a reduction of 91.7% (from 876 mg/l to 73 mg/l), while P. fragii reduced the solid concentration from 876 mg/l to 98 mg/l (88.8%). B. subtilis could only achieve 48.5% reduction in chloride concentration (from 127.08 mg/l to 65.39 mg/l compared to a reduction of 54.6% (from 127.08 mg/l to ...

As a follow-up to our previous study on the transesterification of Nigerian Jatropha curcas oil into Biodiesel using homogenous catalysis, kinetic study of the reaction is hereby presented. The kinetic study revealed that the rate of formation of biodiesel can be increased by increasing reaction temperature and oil to alcohol molar ratio. The optimum reaction condition was established to be 60°C (reaction temperature) and 1:6 (oil to alcohol ratio). Accordingly, the highest biodiesel yield obtained from homogeneously catalyzed transesterification of Nigerian Jatropha curcas (JC) oil into Biodiesel was 86.61% w/w at 60°C with oil to alcohol ratio of 1:6. Furthermore, kinetic study also revealed that conversion of triglyceride to diglyceride was the rate determining step (RDS) of the overall reaction because activation energy of its backward reaction is lower than that of the forward reaction, indicating unstable nature and higher potential energy of the diglyceride in comparison to the triglyceride.

The potential of cashew apple juice (CAJ) as a carbon source for oxalic acid (OA) production via fermentation process was investigated in this study. The effects and interactions of CAJ concentration, time, pH, NaNO3 concentration and methanol concentration on OA production were determined in a central composite design (CCD) and the process was modelled and optimized using response surface methodology (RSM). The results showed that OA fermentation can be described significantly (p < 0.05) by a quadratic model giving regression coefficient (R2) of 0.9964. NaNO3 concentration was the most significant positive variable while methanol was not a significant variable. A maximum OA concentration of 122.68 g/l could be obtained using the optimum levels of CAJ of 150.0 g/l, pH of 5.4, time of 7.31 days, NaNO3 of 2 g/l and methanol of 1% volume. The production of OA was found to increase from 106.75 to 122.68 g/l using the statistically design optimization. This study revealed that CAJ could serve as an inexpensive and abundant feedstock for fermentative OA production, the resulting model could be used in the design of a typical pilot plant for a scale up production.

Date palm is believed to have been introduced into Nigeria in the early 8th century by Arab traders from north Africa. Date fruits are a highly valued delicacy among many communities in Nigeria, especially during ceremonies and festivals. The national consumption of dates in 2009 is estimated at 8,958 metric tons which placed the country among the world top 10 consumers of date. Despite conducive soil and climatic conditions for date palm cultivation and the existance of local varieties with good fruit qualities, date palm cultivation is still at subsistance level and domestic production is estimated at only 1,958 metric tons. Attempts to improve the Nigerian date palm industry through the establishment of commercial date palm plantations have been hindered by lack of good planting materials. However, recent evaluation of the response of some of the Nigerian date palm cultivars to 2,4-D induced callogenesis demontrated the high propensity of the genotypes to in vitro culture, with more than 50% embryogenic callus formation on modified MS supplemented with 50 micrometer 2,4-D in all the genotypes tested. Further research is needed to complete and optimise this protocol in order to solve the problem of date palm planting materials in the country.

The present study investigated the phenol utilization kinetics of a pure culture of an indigenous Pseudomonas fluorescence under steady state and non-steady state (washout) conditions. Steady states of a continuous culture with an inhibitory substrate was used to estimate kinetic parameters under substrate limitation (chemo stat operation) Pure cultures of an indigenous Pseudomonas fluorescence were grown in continuous culture on phenol as the sole source of carbon and energy at dilution rates of 0.010 - 0.20/h. Using different dilution rates, several steady states were investigated and the specific phenol consumption rates were calculated. In addition, phenol degradation was investigated by increasing the dilution rate above the critical dilution rate (washout cultivation). The results showed that the specific phenol consumption rate increased with increased dilution rate at steady state and phenol degradation by Pseudomonas fluorescence can be described by simple substrate inhibition kinetics under substrate limitation but cannot be described by simple substrate inhibition kinetics under washout cultivation. Fitting of the steady state data from continuous cultivation to various inhibition models resulted in the best fit for Haldane, Yano and Koga (2), Aiba and Teissier kinetic inhibition models. The r smax value of 0.229 mg/mg/h obtained from the inhibition model equations was comparable to the experimentally calculated r smax value of 0.246 mg/mg/h obtained under washout cultivation. Therefore, the biokinetic constants evaluated using these models showed good tolerance and growth of the indigenous organism.

There has been considerable interest in the development and production of biodegradable polymer to solve the current problem of pollution caused by the continuous use of synthetic polymer of petroleum origin. Polyhydroxyalkanoates (PHAs) are known to be accumulated as intracellular inclusion in some bacteria. The materials properties exhibited by PHAs, ranging from stiff, brittle to rubber-like makes it a close substitute for the synthetic plastic. The high cost of PHAs production has restricted its applications. The possibility of producing this polymer commercially and at comparable cost has been the main focus in this area. Key Words: Polyhydroxyalkanoates, biodegradable polymer, bioplastic, poly(3-hydroxybutyrate), biosynthesis. African Journal of Biotechnology Vol.3(1) 2004: 18-24

As worldwide adoption of genetically modified crops (GMOs) continues to grow at a double-digit rate, there remains uncertainty, confusion, apprehension, and resistance to the technology in some African countries including Nigeria. Noteworthy, however, is that the Federal Government of Nigeria adopted biotechnology policy in April 2001 and later in November of the same year; the National Biotechnology Development Agency was formed as a parastatal under the Federal Ministry of Science and Technology. The Agency was set up to domesticate and promote modern Biotechnology tools and products. The safe practice of this technology requires a biosafety law in place. The Cartagena Protocol on Biosafety requires parties to it to develop their Biosafety Administrative and Regulatory Framework in order to effectively regulate activities of agricultural biotechnology. A National Biosafety Framework under the UNEP/GEP by the Federal Government of Nigeria, which included, among other things, the National Biosafety Policy Biosafety Bill, was developed in 2006. The House of Representatives and Senate passed the Draft Biosafety Bill in July 2010 and June 2011 respectively. This Bill got transmitted to President Goodluck Ebele Jonathan for assent but was not assented to because the tenure of the National Assembly that passed it ended a day after the Bill got passed. It has been returned to the 7th Assembly, which is in Session right now and receiving attention after which President Goodluck Ebele Jonathan will finally pass it. This paper attempts to present the experience and the road map of the enactment of Biosafety Law in Nigeria.

Thermomyces lanuginosus RT9 was grown in a stirred and aerated reactor for the production of xylan-degrading enzymes and the kinetics of xylanase and β-xylosidase secretion investigated. During each fermentation, k L a decreased with increasing mycelia concentration to the point of cellular disintegration. Although both agitation and aeration rates had significant influences on the growth rate as well as on the yields and rates of enzymes (xylanase and β-xylosidase) release, the enzyme secretion kinetics showed a comparable pattern independent of the operating conditions. Enzyme secretion could be separated into a growth phase, during which extracellular xylanase was at low level, and an enzyme release phase, when there was a notable increase in the xylanase production rate accompanying cellular disintegration.

Data for the anaerobic growth of Klebsiella pneumoniae DSM 2026 and Clostridium butyricum DSM 5431 on glycerol have been analyzed using the concept of material and available electron balances with consideration for hydrogen production. Models for the kinetics of energetic efficiencies of product formation under low residual glycerol are presented. For Klebsiella pneumoniae, the specific rates of electron transfer to the products were mainly significantly dependent on specific growth rate with the exception of ethanol and hydrogen which were also significantly non-growth associated. In the case of Clostridium butyricum, the rates were only growth rate dependent, except for hydrogen formation. The analysis also indicated that the production of 1,3-propanediol by Klebsiella pneumoniae was favoured by limitations other than glycerol limitation, while hydrogen generation was best under low residual glycerol and particularly in the presence of external 1,3-propanediol. Klebsiella pneumoniae appeared to be able to incorporate more of the available electrons of glycerol into hydrogen as compared with the Clostridium butyricum. The study demonstrates the need for properly considering H2 in models describing anaerobic processes.

An estimation of the true growth yields and maintenance coefficients for Comamonas acidovorans DSM 6426 under continuous cultivation on quinoline has been performed. The data were checked for consistency using available electron, carbon and nitrogen balances. The true biomass energetic yields, η max , and energetic maintenance coefficients, me, were estimated using two models based on control of growth rate and control of substrate uptake rate, respectively. The estimations were converted to the various familiar true growth yield and maintenance units such as substrate-based (Y X/S max , m S/X ), oxygen-based (Y X/O2 max , m O2/X ) and carbon dioxide-based (Y X/Co2 max , m CO2/X ) units. For tbe complete mineralization of quinoline by C. acidovorans, values of η max =0.371 and m e =0.0426 h -1 were obtained

Batch reactors were employed to investigate the kinetics of cellulose hydrolysis under extremely low acid (ELA) and high temperature condition. The sawdust was pretreated by Autohydrolysis prior to the batch reaction. The maximum yield of glucose obtained from the batch reactor experiment was about 70% for the pretreated sawdust, this occurred at 210 and 220°C. The maximum glucose yield from the untreated sawdust was much lower at these temperatures, about 55%. The maximum yields of glucose from the lignocellulosics were obtained between 15th and 20th minutes after which gradual decrease was observed.

Simple regression analysis is based on the least square of residual errors. To use this method, an independent variable which is observable without error is assumed to exist. For most analyses, the assumption is normally made without realising the implications. The present study demonstrates how parameters may be estimated with the assumption of error in all measurements. Data sets involving batch/fed-batch cultivation of Candida utilis were analysed using a statistical approach with error in variables for the estimation of true biomass energetic yield and maintenance coefficient. This approach requires replicated measurements. For linear systems, such as in chemical/biochemical processes, replicated measurements are sometimes possible or there are physical/physiological reasons to group the observations into clusters. When clusters of replicated measurements are not available, the cluster analysis technique may be used to identify groups of near-replicated data points. The procedure yielded similar results to those obtained by the ordinary least squares procedure for consistent data. However, for data of poor quality (especially data with large errors in the independent variable), the disparity between the two procedures was more significant.

Product formation during anaerobic degradation of glycerol byKlebsiella pneumoniae DSM 2026, under glycerol limitation and glycerol excess in continugius cultures, has been investigated. Major and minor products and by-products as well as gaseous products were measured. The results indicated a positive correlation between specific glycerol uptake and most product formation rates under glycerol limitation. The production of 1,3-propanediol, lactate, formate, acetate, succinate and the by-products of anaerobic glycerol degradation byK. pneumoniae, acetoin and 2,3-butanediol, was favoured by glycerol excess, while hydrogen generation and ethanol formation were best under glycerol limitation. It was also found that under glycerol limitation the rate of hydrogen evolution was generally higher than the CO2 production rate while under excess glycerol the reverse was true. Hence, on the basis of the ratio of the specific rates of evolution of H2 and CO2 (q H 2/q CO 2), it is possible to infer the existence of glycerol limitation. On the basis of the carbon and available electron balances, which are independent of metabolic pathways, the data are consistent. The NADH2 balance, which took into consideration the pathways of product formation, was also tested to check the validity of the assumed pathways and to check critically the consistency of the data. Good balances were also obtained.[

Analysis of the respiro-fermentive growth of a strain of Saccharomyces cerevisiae, DSM 2155 on glucose, in a simulated 5-phase feeding strategy of fedbatch cultures executed on the Universal BIoprocess CONtrol (UBICON) system, was carried out. There was a good agreement between the estimated and the simulated values of specific growth rates. In this study, which was designed to span 0.20–0.23 h−1 growth rates before returning to lower growth rates, the critical dilution rate at which the switch between purely oxidative and respiro-fermentative growth takes was not observed. The biomass yield, specific substrate uptake and O2 consumption rates as well as the consistency of the data using both carbon and available electron balances were examined. A high average value of true biomass energetic yield, ηmax = 0.707, and a low value of maintenance coefficient, me = 0.0114 h−1, were obtained indicating that the organism was in no danger from the ethanol produced as a high-density fermentation with a yeast concentration above 54 g 1−1 was possible within a period of 24 h. The yeast produced also had good dough-leavening characteristics. Thus it is possible to operate a yeast plant without resorting to using respiratory quotient, which may be problematic, as the controlling parameter.

Analysis of the growth of Pseudomonas cepacia G4 on phenol in continuous culture has been carried out. The data were checked for consistency using both available electron and carbon balances. Coupled with the covariate adjustment estimation technique, the best estimates for true biomass energetic yield, ηmax and maintenance, me, were obtained when the carbon dioxide measurements were excluded. However, upon making corrections to the gas measurements, the best estimates were the maximum likelihood estimates (MLE) based on the complete data. The method therefore allows discrimination to be made between data. Also, similar estimates were obtained using Pirt's model based on the Monod approach and a modified form based on substrate uptake rate being the limiting factor. For the aerobic growth of P. cepacia G4 on phenol, ηmax = 0·417 and me = 0·0513 h−1 were obtained when the CO2 data were excluded. When corrections were made to the gas measurements to take into account the dissolved CO2 and the effect of operating temperature, ηmax = 0·432 and me = 0·0684 h−1 were obtained. From the 95% confidence intervals, a maximum of about 38–47·5% of the energy contained in phenol is incorporated into the biomass while the balance (52·5–62%) is evolved as heat with only a little energy needed for the maintenance of the organism.

The potential of local strains of microorganism ( Pseudomonas fluorescens ) in polyhydroxbutyrate production was investigated in this study. This was with a view to establishing the capabilities of local strains of microorganisms on utilizing renewable and locally available substrates in polyhydroxybutyrate production. This involved hydrolysis of starch extracted from freshly harvested cassava tubers using enzyme-enzyme method of hydrolysis, followed by aerobic fermentation of Pseudomonas fluorescens on a mixture of the hydrolysate and nutrient media in a fermentor in batch cultures. The reducing sugar hydrolysate served as the carbon source and diammonium sulphate as the limiting nutrient. The reaction temperature, pH and agitation rate in the fermentor were maintained at 30°C, 7.5 and 400 rpm respectively. The biomass growth was measured by cell dry weight and the polyhydroxybutyrate content measured by gas chromatography. When the fermentation process was shut down after 84 hour, the substrate consumption by the organism was 9.2 g/L to give a dry cell weight of 1.75 g/L resulting in a biomass yield on substrate (Y x/s ) of 0.1902 g/g (19.02 % wt/wt). The gas chromatographic analysis gave a final polyhydroxybutyrate value of 1.254 g/L with corresponding product yield on biomass (Y p/x ) of 0.7166 g g -1 [71.66% wt/wt] and product yield on substrate (Y p/s ) of 0.1363 g g -1 [13.63% wt/wt]. The results show that the organism accumulated polyhydroxybutyrate in excess of 50 % of the cell dry weight by giving a final polyhydroxybutyrate yield on biomass (Y p/x ) of 0.7166 g g -1 [71.66% wt/wt] which agrees with the general trend in polyhydroxybutyrate production. @ JASEM J. Appl. Sci. Environ. Manage . December, 2010, Vol. 14 (4) 61 - 66

Data collected during the high-cell-density cultivation of Saccharomyces cerevisiae DSM 2155 on glucose in a simulated five-phase feeding strategy of fed-batch process, executed on the Universal BIoprocess CONtrol (UBICON) system using 150L bioreactor over a period of 24h have been analysed. The consistency of the data set was checked using both the available electron and carbon balances. Estimates of the true energetic yields and cell maintenance requirements were obtained through the application of a multivariate statistical procedure known as covariate adjustment technique. A low value of maintenance coefficient, me = 0.004h-1, and a high average value of the true biomass energetic yield, hmax = 0.745, were obtained for the bioreactor system, which showed that the organism was in no danger of ethanol produced during this cultivation. A simple model for estimating the distribution of substrate consumed between the fermentative and the respiratory pathways in the oxido-reductive process was developed based on the respiratory quotient (RQ) values. The fraction of substrate consumed for respiratory metabolic activities (qsresp/qs) was virtually 1.0 for the first three phases of the feeding strategy, which accounted for the first sixteen hours of the 24h operation. This was an indication that ethanol formation was avoided during this period. (African Journal of Biotechnology: 2003 2(5): 96-103)

The objective of this study was to estimate and analyse the growth parameters of indigenous monoculture of Pseudomonas aeruginosa and Pseudomonas fluorescence on phenol in an aerobic chemostat culture. The biodegradation data were checked for consistency using carbon and available electron balances and growth parameters were estimated using two forms of growth models: reparameterised Pirt’s model based on Monod approach and a modified model based on substrate consumption rate. The results showed that the biodegradation data were consistent; growth parameter estimates using the two forms of models were similar and that phenol could be oxidatively metabolised with a maximum of about 35.4%–36% and 31%–33% of the energy contained in it incorporated into the P. aeruginosa and P. fluorescence biomass, respectively. The balance (63%–64.6%) for P. aeruginosa, and (67%–69%) for P. fluorescence, is evolved as heat with little energy needed for the maintenance of the respective organisms.

The potential of various organisms to metabolise organic compounds has been observed to be a potentially effective means in disposing of hazardous and toxic wastes. Phenolic compounds have long been recognised as one of the most recalcitrant and persistent organic chemicals in the environment. The bioremediation potential of an indigenous binary mixed culture of Pseudomonas aeruginosa and Pseudomonas fluorescens was studied in batch culture using synthetic phenol in water in the concentration range of 100?500 mg/litre as a model limiting substrate. The effect of initial phenol concentration on the degradation process was investigated. Phenol was completely degraded at different cultivation times for the different initial phenol concentrations. Increasing the initial phenol concentration from 100 mg/litre to 500 mg/litre increased the lag phase from 0 h to 18 h and correspondingly prolonged the degradation process from 24 h to 96 h. There was decrease in biodegradation rate as initial phenol concentration ...

Bioenergetic analysis of the growth of Pseudomonas fluorescens on phenol chemostat culture was carried out. The data were checked for consistency using carbon and available electron balances. Similar estimates were obtained using Pirt's model based on Monod approach and a modified model based on substrate consumption rate being rate limiting. Coupled with the covariate adjustment estimation technique, the best estimates were the Maximum Likelihood Estimates (MLE) based on the complete data. For the aerobic growth of P. fluorescens growth on phenol, ηmax = 0.262 and me = −0.017/h. From the 95% confidence intervals, a maximum of about 25?27% of the energy contained in phenol is incorporated into the P. fluorescens biomass. The balance (73?75%) is evolved as heat with little or no energy needed for the maintenance of the respective organisms.

The removal efficiency of phenol from aqueous solutions was measured using an indigenous freely suspended binary mixed culture of Pseudomonas aeruginosa and Pseudomonas fluorescens. Experiments were performed as a function of temperature (25?45°C), aeration (1.0?3.5 vvm) and agitation (200?600 rpm). Optimisation of these three process parameters for phenol biodegradation was studied. Statistically designed experiments using response surface methodology were used to get more information about the significant effects and the interactions between the three parameters. A 2³ full-factorial central composite design followed by multistage Monte Carlo optimisation technique was employed for experimental design and analysis of the results. The optimum process conditions of temperature 30°C, aeration 3.0 vvm and agitation 300 rpm were recognised for maximising phenol degradation (removal). Maximum removal efficiency of phenol was achieved (100%) at the optimum process conditions.

The potential of microorganisms to catabolise and metabolise xenobiotic compounds has been recognised as a potentially effective means of toxic and hazardous wastes disposal. Phenol and its derivatives have long been recognised as some of the most persistent chemicals in petroleum refinery wastewaters, with high toxicity even at low concentrations. Biodegradation of these compounds has been recognised as a potential solution for their disposal owing to its cost effectiveness and simplicity. Two species of pseudomonas, P. aeruginosa and P. fluorescence, were studied for their biodegradation potential on phenol present in a refinery wastewater under a batch fermentation process. Phenol was successfully degraded by both species, and there was high positive correlation between phenol biodegradation and microbial growth. The maximum specific growth rate were obtained for both species from the Haldane model. The study revealed the high potential of these local strains, with P. aeruginosa being more effective, and the possibility of using them in bioremediation of petroleum refinery wastewaters.

The microbial degradation of phenols has been reviewed including the phenol-degrading microbes, factors affecting degradability, and the use of biotechnology with emphasis on degradation mechanisms and their kinetics. The mechanism of microbial degradation depends on aerobic and anaerobic conditions. Under aerobic conditions, degradation of phenol was shown to be initiated by oxygenation into catechols as intermediates followed by a ring cleavage at either the ortho or meta position, depending on the type of strain. Anaerobic biodegradation of phenol occurs by carboxylation followed by dehydroxylation (reducing reaction) and dearomatisation. It was also clear that the parameters used in the Haldane model are not constants but vary, hence it may never be possible to describe the kinetic properties of a microbial cell with a single set of constants.

Analysis of the growth of Trichosporon cutaneum on glucose was carried out using the concepts of material and energy regularities. Carbon and available electron balances were used to check the consistency of the measured data and to detect outlying data points. Combined point and interval estimates of the true biomass energetic yield and maintenance coefficient for T. cutaneum were obtained using a multivariate statistical procedure. The analysis shows that T. cutaneum has a higher true biomass energetic yield and a lower maintenance coefficient than Candida utilis, which has been found suitable for SCP production.

This work is concerned with the application of material and energy balances in an attempt to understand the phenomenon of product build-up when Pseudomonas aeruginosa is grown on n-hexadecane in a batch fermentor. It is shown that the organism accumulates a polyactide, called poly-B-hydroxybutyrate (PHB) during early stages of growth and metabolizes it at later stages of growth. This explains the low carbon and available electron balances which have been observed.

When more than the minimum number of variables are measured, and measurement error is taken into account, the results of parameter estimation depend on which of the measured variables are selected for this purpose. The reparameterization of Pirt's models for growth produces multiresponse models with common parameters. By using the covariate adjustment technique, a unit variate linear model with covariates is obtained. This allows a combined point and interval estimates of biomass energetic yield and maintenance coefficient to be obtained using standard multiple regression programmes. When this method was applied using form I and form II of the Pirt's models, good combined estimates were obtained and compared. Using data from the literature for Candida lipolytica produced reliable results. However, for Pseudomonas aeruginosa, which has been known to produce intermediate products, a modified Pirt's model is required for a good estimate of the biomass energetic yield.

The effect of high-dose irradiation as a pretreatment method on two common lignocellulosic materials; hardwood (Khaya senegalensis) and softwood (Triplochiton scleroxylon) were investigated by assessing the potential of cellulase enzyme derived from Aspergillus flavus Linn isolate NSPR 101 to hydrolyse the materials. The irradiation strongly affected the materials, causing the enzymatic hydrolysis to increase by more than 3 fold. Maximum digestibility occurred in softwood at 40kGy dosage of irradiation, while in hardwood it was at 90kGy dosage. The results also showed that, at the same dosage levels (p < 0.05), hardwood was hydrolysed significantly better compared to the softwood.

Bagasse, corncob and sawdust were used as lignocellulosic substrates for the production of cellulase enzyme using Aspergillus flavus after ballmilling and pretreatment with caustic soda. From the fermentation studies, sawdust gave the best result with an enzyme activity value of 0.0743IU/ml while bagasse and corncob gave 0.0573IU/ml and 0.0502IU/ml respectively. The three lignocellulosics gave their maximum enzyme activities at about the twelfth hour of cultivation, suggesting that the 12th hour is the optimum time when the enzyme may be harvested. (African Journal of Biotechnology: 2003 2(6): 150-152)

Cashew juice was investigated for its ability to support the growth of Saccharomyces cerevisiae. A characteristic of the juice showed that it contained a mixture of fermentable sugars of which glucose, fructose and sucrose have been identified. Also the concentration of reducing sugars was as high as 15% w/v. Growth studies were carried out in a 7-L batch fermentor at a pH of 5.0 and 30°C with and without nutrient supplementation. The corresponding yields were 0.50 and 0.39 gram cells/gram reducing sugar consumed, respectively. While about 10% of the reducing sugar was consumed in the unsupplemented medium 43% was consumed in the medium with supplementation.