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The objective of the present study was the restoration of sterilized soil contaminated with atrazine (5.52 mg kg−1) using atrazine-degrading bacteria, biochar, and poultry manure amendments. The atrazine-degrading bacterium was purified from a mixed culture isolated from a long-history atrazine soil, and identified as Alcaligenes sp. strain AZUHUB-A31-CH52 ND4 based on the 16S rRNA sequence. After 35-day bioremediation, the sterile soil inoculated with Alcaligenes sp. and amended with biochar or poultry manure improved atrazine removal efficiency (98–99%) while the soil containing only atrazine degraders resulted in the lowest atrazine removal (78%). The atrazine degradation kinetics in the amended and unamended soils adequately fit the double first-order in parallel (DFOP) model given the goodness of fit parameters (high r2 (0.9703–0.9997) and low AICc (−106.30 to −28.92) values. The DFOP model also predicted that DT50 (half-life) in all treatments was < 1 day (0.03–0.13 day) at a fast dissipation rate k1 (5.422–20). The DT90 (90% atrazine removal) estimated by DFOP ranged between 23–94 days. The results demonstrated that low-cost bio-waste could offer a sustainable and eco-friendly approach for the reclamation of soils contaminated with atrazine.

Biosurfactants – tensioactive biometabolites – are currently preferred over their synthetic counterparts due to some unique properties such as sustainable production, eco-compatibility, and low cytotoxicity, among others. Among different biosurfactant groups currently known, the microbial-derived glycolipids (MGLs) are of growing interests in the formulation of biomedical and cosmetic products due to their structural diversities, antimicrobial properties, stability under harsh environmental conditions, and functional versatility. While the usefulness of the MGLs in biomedical and cosmetics fields cannot be overemphasized, their commercial competitiveness has been restrained due to a myriad of bottlenecks which include poor product yields and high cost of production associated with downstream processing. Herein, we reviewed the importance of process economics in MGLs production to project strategies needed for product competitiveness in terms of yields and cost which will favour their global market. The significance of techno-economic assessment in translating laboratory-based data to commercial-scale MGL production was underlined. The strategies adopted by commercial MGL-producing firms to enhance the market value of their products were also presented. Finally, the future of MGLs in the surfactant market is highlighted.

The therapeutic application of bromelain is limited due to its sensitivity to operating conditions such as high acidity, gastric proteases in the stomach juice, chemicals, organic solvents and elevated temperature. We hypothesized that bromelain immobilized on probiotic bacterial spores would show enhanced therapeutic activity through possible synergistic or additive effects. In this study, the oedema inhibition potential of bromelain immobilized on probiotic Bacillus spores was compared to the free enzyme using the carrageenan paw oedema model with Wistar rats. In batch A rats (carrageenan-induced inflammation 30 min after receiving oral treatments), group 7 rats treated with a lower dose of spore-immobilized bromelain suspension showed the highest oedema inhibition, 89.20 ± 15.30%, while group 4 treated with a lower dose of free bromelain had oedema inhibition of 60.25 ± 13.00%. For batch B rats (carrageenan-induced inflammation after receiving oral treatment for three days), group 7 rats treated with a lower dose of spore-immobilized bromelain suspension showed higher inhibition percentage (81.94 ± 8.86) than group 4 treated with a lower dose of free bromelain (78.45 ± 4.46) after 24 h. Our results showed that used alone, the enzyme and the spores produced oedema inhibition and improved the motility of the rats. The spore-immobilized bromelain formulation performed approximately 0.9-fold better than the free bromelain and the free spores at the lower evaluated dose.

Weak acids are known to have a negative impact on yeast performance, restraining production efficiency during the production of bioethanol and other fermentative yeast-derived products. These acids, which might be hydrophilic or lipophilic exert negative effects on yeasts when they diffuse into the cell in their unionized state as a result of their pH being lower than the pka of yeast growth medium. Consequently, the unionized acids dissociate into their respective cations and anions, as intracellular pH is typically neutral. Further, proton accumulation tends to reduce intracellular pH. As a result, the anions destabilize the internal cell machinery, thus affecting cellular metabolism on various levels. Overcoming this acid-mediated stress in budding yeast would in part, harness the potential of using lignocellulosic biomass hydrolysate – which is typically acetic acid-rich – as a cheaper feedstock for large-scale bioethanol production. Since organic acids are key intermediates in ethanol fermentation, this review focuses on the prospects of bioethanol production from lignocellulosic biomass using weak acid-tolerant strains of yeasts derived by metabolic engineering.

Mass transfers pose significant challenge in fermentation due to wide diffusion gradient existing between the culture broth and the immobilized cells. In the present study, Saccharomyces cerevisiae LC 269108 was immobilized in a recently described microporous alginate beads. The new method was compared with the conventional calcium alginate gel beads in a repeated batch process for the production of ethanol. The fermentation conditions implemented were 110 rpm, pH 5.5 and temperature of 30°C for 60 h. The bead diameters were 3 mm while the calcium chloride concentration was 2.0%. In separate batch experiments conducted by the simultaneous saccharification and fermentation (SSF) method, the free cells maintained plateau at peak ethanol concentration of 7.50±0.33% after 36 h. In the conventional alginate (6.51±0.05%) and microporous beads (7.06±0.10%), ethanol dropped in concentration until reaching final volumes of 5.65±0.33 and 6.56±0.64%, respectively. In the repeated batch experiments, five fermentation batches or runs were conducted over a 12 h period each. The concentrations of ethanol produced in batches with the cells immobilized in calcium alginate were 2.91±0.34, 5.80±0.22, 5.01±0.39, 4.41±0.14 and 3.77±0.21%, respectively. Cells immobilized in microporous beads had higher ethanol output with concentrations 2.33±0.07, 6.62±0.04, 6.16±0.32, 5.90±0.2 and 4.70±0.26% obtained after five respective batches. Glucose metabolism was found to be lower with cells immobilized in alginate beads. From initial glucose concentration of 14.30±0.2%, residual glucose was detected after the first (3.61±2.11%), fourth (3.18±0.98%) and fifth (5.30±0.86%) batches of fermentation. In the batches containing microporous beads, residual glucose (5.36±0.29%) was confirmed after the first batch only. The present study demonstrates the feasibility of using microporous beads in the production of ethanol. Key words: Mass transfer; microporous beads, immobilized cells, ethanol, calcium alginate.

We investigated a number of microbiological activities in the soil to serve as biomonitoring tools in assessing the ecotoxicity of diesel-contaminated soil samples during the different periods of bioremediation. Sawdust was used as the biostimulant for the biodegradation of artificial diesel-polluted soil samples. Soil microbial population, soil microbial enzymatic activities (catalase, lipase, dehydrogenase, urease, phosphatase and β-glucosidase), soil microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP), soil microbial respirometric index and total petroleum hydrocarbon (TPH) concentration were monitored to evaluate the efficiency of the bioremediation process. After a period of 56 d, total petroleum hydrocarbon content reduced from 14,221 to 270 mg/kg. The parameter estimation using the nth-order kinetic model revealed that the first-order rate constants (

The transition from a fossil-based linear economy to a circular bioeconomy is no longer an option but rather imperative, given worldwide concerns about the depletion of fossil resources and the demand for innovative products that are ecocompatible. As a critical component of sustainable development, this discourse has attracted wide attention at the regional and international levels. Biorefinery is an indispensable technology to implement the blueprint of the circular bioeconomy. As a low-cost, non-waste innovative concept, the biorefinery concept will spur a myriad of new economic opportunities across a wide range of sectors. Consequently, scaling up biorefinery processes is of the essence. Despite several decades of research and development channeled into upscaling biorefinery processes, the commercialization of biorefinery technology appears unrealizable. In this review, challenges limiting the commercialization of biorefinery technologies are discussed, with a particular focus on biofuels, biochemicals, and biomaterials. To counteract these challenges, various process intensification strategies such as consolidated bioprocessing, integrated biorefinery configurations, the use of highly efficient bioreactors, simultaneous saccharification and fermentation, have been explored. This study also includes an overview of biomass pretreatment-generated inhibitory compounds as platform chemicals to produce other essential biocommodities. There is a detailed examination of the technological, economic, and environmental considerations of a sustainable biorefinery. Finally, the prospects for establishing a viable circular bioeconomy in Nigeria are briefly discussed.

Antibiotic residues together with non-antibiotic drugs and heavy metals act as a selective pressure for the spread of antibiotic-resistant microorganisms (ARMs), antibiotic-resistant genes (ARGs), and mobile genetic elements (MGEs) during composting of livestock manure. ARMs, ARGs and MGEs have become emerging contaminants since they are regularly implicated in the majority of compost produced from livestock manure. The prevalence of these contaminants in agricultural soil receiving compost has drawn huge attention globally due to the risks they pose to the total environment. Although a large body of literature exists on the application of composting methods in minimizing the relative abundance of these contaminants, there is a paucity of information on the robustness, limitations and opportunities and threats of various composting protocols currently deployed. To address this knowledge gap, the current review compiled literature on the origin and mechanisms of the proliferation of ARMs, ARGs, and MGEs during composting of livestock manure. The effectiveness of current composting protocols in the reduction or removal of emerging contaminants was evaluated. Furthermore, the potential environmental impacts and human health risks of these contaminants following land application of compost were also presented. Finally, we propose some strategic approaches for the reduction of ARGs and MGEs during composting of livestock manure.

Background The involvement of probiotic cultures in food fermentation guarantees enhanced organoleptic properties and maximum consumer health benefits. In this study, isolated Bacillus cultures used in the fermentation of African locust bean seeds “Parkia biglobosa” into the food condiment “daddawa” were evaluated for probiotic attributes. Bacillus cereus strains BC1 and BC2 were tested for tolerance to acid, common salt (NaCl), and bile salt. Auto-aggregation and adhesion to epithelial cells, antibiotic sensitivity profile, hemolytic pattern, and antibacterial activity were also evaluated. To demonstrate further health benefit, spores of strain BC1 were investigated for anti-inflammatory potential employing the rat paw edema technique. Results Both Bacillus cereus strains showed antagonistic activity against pathogenic Escherichia coli and Staphylococcus aureus. BC1 was more acid-stress tolerant than BC2, maintaining 107.6% viability after 3 h incubation in MRS broth of pH 2.5. However, at 97.74% viability after incubation for 3 h, BC2 was more tolerant to 0.4 % bile salt. The Bacillus cereus strains were susceptible to all antibiotics tested with the exception of norfloxacin and thrived under high saline stress. Both strains were protease producers and non-hemolytic on sheep blood agar. The edema inhibition study revealed that spores of Bacillus cereus strain BC1 had anti-inflammation potential and produced no physiological toxicity on the animals. Conclusion These results indicate that the Bacillus cultures for “daddawa” production are good candidates for probiotics and have the potential for application in both animal and human formulations for increased health benefit to consumers.

The effective recovery of organic waste through composting has provided mankind with a multipurpose product (compost) which, apart from being used as biofertilizer and biopesticide, can find application in erosion management and restoration of hydrocarbon-polluted soil. Interestingly, composting technology could be indispensable in the actualization of sustainable agriculture due to its environmental friendliness, cost-effectiveness, and sustainability. However, for the essential concepts of sustainable agriculture—care, health, fairness, and ecology—to be realized, the composting process should be effectively managed. Therefore, in this chapter, we addressed the various methods of composting management, challenges, and application in agriculture.

Anaerobic digestion (AD) of poultry wastes is considered one of the best alternatives for handling the current problematic task of managing these wastes, usually produced in large proportions globally, leading to energy and high nutrient recovery. This chapter highlights some of the environmental issues arising from current management strategies of poultry wastes. Further, it discusses the processes involved in the AD of poultry wastes as well as the value-added products that can be generated from the process. This review also includes the technoeconomic analysis of the process and some challenges arising from the environmental assessment of AD. Finally, critical areas for further consideration involved in the AD of poultry wastes are highlighted.

Environmental pollution mitigation measure involving bioremediation technology is a sustainable intervention for a greener ecosystem biorecovery, especially the obnoxious hydrocarbons, xenobiotics, and other environmental pollutants induced by anthropogenic stressors. Several successful case studies have provided evidence to this paradigm including the putative adoption that the technology is eco-friendly, cost-effective, and shows a high tendency for total contaminants mineralization into innocuous bye-products. The present review reports advances in bioremediation, types, and strategies conventionally adopted in contaminant clean-up. It identified that natural attenuation and biostimulation are faced with notable limitations including the poor remedial outcome under the natural attenuation system and the residual contamination occasion following a biostimulation operation. It remarks that the use of genetically engineered microorganisms shows a potentially promising insight as a prudent remedial approach but is currently challenged by few ethical restrictions and the rural unavailability of the technology. It underscores that bioaugmentation, particularly the use of high cell density assemblages referred to as microbial consortia possess promising remedial prospects thus offers a more sustainable environmental security. The authors, therefore, recommend bioaugmentation for large scale contaminated sites in regions where environmental degradation is commonplace.

Despite the impressive gain in agricultural production and greater availability of food, a large portion of the world population is affected by food shortages and nutritional imbalance. This is due to abiotic stresses encountered by plants as a result of environmental-driven perturbations, loss of viability of starter cultures (probiotics) for functional foods during storage as well as the vulnerability of farm produce to postharvest pathogens. The use of compatible solutes (e.g., trehalose, proline, etc.) has been widely supported as a solution to these concerns. Trehalose is one of the widely reported microbial- or plant-derived metabolites that help microorganisms (e.g., biocontrol agents, probiotics and plant growth-promoting bacteria) and plants to tolerate harsh environmental conditions. Due to its recent categorization as generally regarded as safe (GRAS), trehalose is an essential tool for promoting nutrition-sensitive agriculture by replacing the overuse of chemical agents (e.g., pesticides, herbicides). Therefore, the current review evaluated the progress currently made in the application of trehalose in sustainable agriculture. The challenges, opportunities, and future of this biometabolite in food security were highlighted.

In the present study, we investigated the effects of inorganic nitrogen sources—(NPK fertilizer, 15:15:15), (urea fertilizer, 46:0:0), (NH4)2SO4 as well as monitored natural attenuation on the bior...

Herein, we conducted a study toward understanding the impact of composting of the diesel-contaminated soil with some locally available bulking agents (rice husks (RHs), sawdust (SD), and wood chips (WCs)). In order to ascertain the effectiveness of petroleum degradation by the process assayed, we compared the protocols with monitored natural attenuation (MNA). The overall degradation pattern was modeled with non-linear regression by comparing the experimental data with first and second-order kinetic equations. At the end of the six-week study, the amount of total petroleum hydrocarbon removed from contaminated soil was 98.26 ± 1.33% (amendment with SD + RHs + WCs), 96.89 ± 1.20 (RHs amendment), 96.55 ± 1.29% (amendment with SD), 90.01 ± 0.22% (WCs amendment), and 85.02 ± 0.21% (MNA). The degradation of TPH trends followed a second-order kinetic model for all the four compost treatments while the MNA was found to follow a first-order (slower) degradation pattern. In general, the results of the para...

Advocating production of bio-energy from agricultural crop wastes has double benefits of minimizing land usage and threat to food security. These benefits are specially needed now that issues of greenhouse emissions, deforestation and human over population of the world dominate international discuss. Cassava being a major food crop in Africa, its waste constitutes the major candidate for bio-energy production thus motivating the aim to review its history, production, food value, economic value and bio-energy value. Cassava waste is noted to be suitable feedstock for bio-fuel production from the 1st Generation, 2nd Generation and integrated processes unlike the other Nigerian crop residues that are mainly suitable for the not-yet-viable 2nd Generation bio-fuel production. A procedure for estimating cassava non-food biomass(CnFB) from harvest data is established. The procedure entails use of statistical sampling and regression analysis to establish scaling factors for transforming the data to CnFB. A real case study reflected very accurate and statistically significant error indices. For example, the factor for converting mass of harvested cassava for food production to waste is R w = 0.5263 (R2 = 0.9875 and t-Test = 0.0896) while the factor for estimating mass of peels alone is R 12 = 0.1735 (R2 = 0.9951 and t-Test = 0.1680). The other factors for converting mass of dewatered cassava pulp to waste were established for the case study community as follows; m w = 33.7675 Kg per bag (R2 = 0.9611 and t-Test = 0.0665), m 3 = 32.0599 kg per bag (R2 = 0.9865 and t-Test = 0.1944) and r w = 1.0508 (R2 = 0.9464 and t-Test = 0.2539). The factors and literature data were used to make long-term projections of CnFB potential of Nigeria. The implications of the projections to the programs of the Nigeria Energy Policy - which pertain to renewable energy integration in the national energy mix, emission reduction and rural electrification via distributed generation - were discussed.

Composting technology has become invaluable in stabilization of municipal waste due to its environmental compatibility. In this review, different types of composting methods reportedly applied in waste management were explored. Further to that, the major factors such as temperature, pH, C/N ratio, moisture, particle size that have been considered relevant in the monitoring of the composting process were elucidated. Relevant strategies to improve and optimize process effectiveness were also addressed. However, during composting, some challenges such as leachate generation, gas emission and lack of uniformity in assessing maturity indices are imminent. Here in, these challenges were properly addressed and some strategies towards ameliorating them were proffered. Finally, we highlighted some recent technologies that could improve composting.

Bioaugmentation can occur either by the use of a single strain microorganism or between different microorganisms (fungi and bacteria). In the present study, we carefully evaluated these two bioaugmentation forms on the degradation of total petroleum hydrocarbon (TPH) in gasoline polluted soil. Microbial activity indexed by dehydrogenase (DHA) assay and effect of pH on biodegradation were also measured. After 8 week incubation, all the studied systems showed varying degree of TPH removal from the gasoline polluted soil. Highest percentage of degradation (75.70%) was observed in Micrococcus luteus, 71.10% in Rhizopus arrhizus and 66.40% in the consortium though removal efficiencies were not statistically different among the bioaugmentation options but differed significantly with the control at p 0.05 . The natural attenuation (control) system had the least TPH removal efficiency (54.04%). The study reported that bioaugmentation involving microbial consortium resulted in initial accelerated biodegradation rates. Fungi bioaugmented systems had low pH condition throughout the experiment. Results of microbial dynamics showed that population density of total heterotrophic microorganisms were higher than actual gasoline degraders and studies using kinetic parameters supported that significant gasoline hydrocarbon removal occurred in the bioaugmentation systems.

Cellulase is an enzyme produced by fungi, bacteria, protozoa and termite, that hydrolyze cellulose. They are known for their diverse applications in industry and medicine. The aim of this study is to purify and investigate cellulolytic properties of cellulase enzyme produced by Bacillus sphaericus CE-3 isolated from refuse dump in Nnamdi Azikiwe University, Awka, Nigeria. Enzyme was produced by submerged fermentation at 30°C for 30 h. The enzyme was purified to homogeneity by dialysis in 4M sucrose solution, ion-exchange chromatography on Q-Sepharose FF and by hydrophobic interaction chromatography on Phenyl Sepharose CL-4B. The relative molecular mass of the enzyme was estimated using SDS-Polyacrylamide gel electrophoresis. Effects of temperature, pH and metals on enzyme activity and stability and the relative rate of hydrolysis of various substrates were also studied. The Purification fold for the enzyme was 7.8, with 66.4 μ/mg specific activity protein and overall yield of 35.8. The relative molecular mass range of the enzyme was estimated between 22.3 kDa - 26.3 kDa. The enzyme was optimally active at pH 9.0 and 40°C, stable at pH 9.0 and unusually retained over 90% activity between 50°C - 100°C after 30 min incubation. It was strongly activated by Mn2+ but inhibited by Ba2+, Co2+, Hg2+, Pb2+, Cu2+, Sr2+, Fe2+, Ca2+ and Zn2+. The cellulase displayed high catalytic activity with untreated sawdust, followed by carboxymethyl cellulose, while sodium hydroxide treated sawdust was the least hydrolyzed. Since the enzyme is thermo-stable, alkalophilic and could utilize natural wastes like sawdust as substrate, it is obvious that it would be of great use in textile, starch processing and pulp and paper industries.

Soil pollution by petroleum hydrocarbons no doubt has become an issue of contemporary concern. Different remediation technologies have been used to tackle these hydrocarbon spillage problems each regrettably with its own shortcomings. Hydrocarbon removal by bioremediation has become the most suitable alternative spill clean-up strategy. Biostimulation, natural attenuation and bioaugmentation are three practical approaches most frequently used to respond to oil spillage cases. Bioaugmentation technology has significantly recorded numerous successes and has also been proven most reliable and most effective. Bioaugmentation though as efficient and most reliable as stated is however not without its own limitations including the problem of initial adaptation of the introduced microbial species in the soil microcosms, temperature, pH and other abiotic factors. Other factors such as predation and competition between the autochthonous and allochthonous microbial communities thus resulting in poor remediat...

Evaluation of rice husk (RH) as bulking agent in bioremediation of automobile gas oil (AGO) hydrocarbon polluted agricultural soil using renewal by enhanced natural attenuation (RENA) as control was the subject of the present investigation. The effect of different parameters such as total petroleum hydrocarbon (TPH), dehydrogenase activity (DHA), optical density and pH on bioremediation performance were evaluated. The studied parameters such as microbial dynamics, percentage degradation and DHA were found to be higher in RH-amended system and differed significantly with control at P < 0.05. RH resulted in high removal efficiency of 97.85 ± 0.93% under a two-month incubation period, while RENA had lesser removal efficiency of 53.15 ± 3.81%. Overall hydrocarbon biodegradation proceeded very slowly in the RENA particularly from week 0 to 4. Experimental data perfectly fitted into the first-order kinetic and generated high r2 values (0.945), first-order degradation constant (0.47 day−1), and shorter d...

Increased demand for electrical and electronic equipment as well as a reduction in the end of life of most electrical products has led to the generation of large amount of E-waste. These wastes contain both beneficial and hazardous components. Therefore, there should be proper management of E-waste in order to protect man and the environment. In this review, we addressed the various categories deployed towards effective E-waste management such as collection and disposal of dangerous portions and recovery of precious metals and energy. The benefits, challenges and future of E-waste management were also highlighted.

Multienzyme complex has attracted increased attention in biofuel technology. They offer solutions to effective degradation of complex plant material into fermentable sugars. Microorganisms, especially bacteria and fungi, are well studied for their ability to produce enzymes complex unlike yeast. Yeast strain isolated from mushroom farm was studied for simultaneous production of cellulase, xylanase and ligninase enzymes using lignocellulose waste as substrates. A response surface methodology (RSM) involving Box-Behnken design (BBD) was used to investigate interaction between variables (moisture content, inoculum size, initial pH, incubation time) that affect enzyme production. Crude filtrate was partially purified and characterised. Yeast strain identified as Saccharomyces cerevisiae SCPW 17 was finally studied. Evaluation of lignocellulose waste for enzyme complex production revealed corn cob to be most effective substrate for cellulase, xylanase and ligninase production with enzyme activity of 17.63 ± 1.45 U/gds, 29.35 ± 1.67 U/gds and 150.75 ± 2.01 μmol/min respectively. Time course study showed maximum enzyme complex production was obtained by day 6 with cellulase activity of 12.5 U/gds, xylanase 48.3 U/gds and ligninase 90.8 μmol/min. Using RSM involving BBD, maximum enzyme activity was found to be 19.51 ± 0.32 U/gds, 56.86 ± 0.38 U/gds, 408.17 ± 1.04 μmol/min for cellulaase, xylanase and ligninase respectively. The developed models were highly significant at probability level of P = 0.0001 and multiple correlation co-efficient (R2) was 0.9563 for cellulase, 0.9532 for xylanase and 0.9780 for ligninase. Enzyme complex was stable at varying pH and temperature conditions. Saccharomyces cerevisiae (SCPW 17) studied produced enzyme complex which can be used for bioconversion of biomass to value-added chemicals., Bioinformatics; Biotechnology; Cell biology; Genetics; Microbiology; Molecular biology; Multienzyme complex, Cellulase, Xylanase, Ligninase, Corncorb, Saccharomyces cerevisiae

Anaerobic digestion (AD) of organic substrates for biogas production is constantly challenged by some critical factors (ammonia inhibition, hydrogen partial pressure and volatile fatty acid accumulation) which result in digester imbalance or failure. This review was undertaken to address how these critical perturbations have challenged AD-derived bioenergy. The key advances (e.g., early warning indicators) for the detection and informing the operators of the digester imbalance such as VFA/alkalinity measurements, e-nose (metal oxide), biogas isotopic labelling and volumetric loading rate and/or VFA saturation estimation were addressed. The novel strategies towards the alleviation of the perturbation causing anaerobic digester dysfunction such as use of multi-stage digesters, use of super high rate systems, introduction of pure microbial cultures and deployment of direct interspecies electron transfer (conductive materials) and statistical modelling are also presented. While some of these approaches are promising in real applications (especially those that are currently at pilot-scale operation), others have been attempted theoretically or shown no recorded success. Considering the varying success in mitigating these challenges, the practical implications of the current study and the future prospects were highlighted.

In the present study, laboratory scale biogas production from rice husks (RH) generated from different rice mills was investigated using cow rumen fluid as a source of inoculum. The effects of various parameters such as water dilution, initial pH, heavy metals and nitrogen sources on digester performance were evaluated. Feedstock to water dilution ratio of 1:6 w/v and initial pH 7 gave the maximum biogas yield of 382 and 357 mL/day, respectively. Addition of heavy metals (Ni2+, Zn2+, and Cu2+) enhanced digester performance with Ni2+ (100 ppm) giving the best biogas yield. The maximum values of biogas production rate were 30 and 69 mL/day for the control and poultry droppings, respectively, after two days while urea gave 8 mL/day on day four. The use of poultry droppings (PD) as nitrogen supplements encouraged biogas generation. Therefore, rice husks offer an alternative source of energy to agricultural farmers.

Pseudomonas nitroreducens MILB-8054A isolated from petroleum-contaminated soil, immobilized on calcium alginate beads, and under resting cell condition, produced biosurfactants. Immobilized cells gave a best yield of 5.6 g rhamnolipid l−1 using sucrose as carbon source. Time course study using resting cells showed that 2 % v/v of palm oil (preculture carbon source) and 10 % diesel (carbon source) gave the best rhamnolipid yield of 5.1 g l−1 at pH 8 and temperature of 30 °C. Carbon utilization by resting cells was compared with that of growing cells. The best biosurfactant recovery procedure was acetone extraction.

Rhamnolipid biosurfactant production by Pseudomonas nitroreducens isolated from petroleum-contaminated soil was investigated. The effects of carbon, nitrogen and carbon to nitrogen ratio on biosurfactant production were examined using mineral salts medium as the growth medium. The tenso-active properties (surface activity and critical micelle concentrations of the produced biosurfactant were also evaluated. The best carbon source, nitrogen source were glucose and sodium nitrate giving rhamnolipid yields of 5.28 and 4.38 g l(-1), respectively. The maximum rhamnolipid production of 5.46 g l(-1) was at C/N (glucose/sodium nitrate) of 22. The rhamnolipid biosurfactant reduced the surface tension of water from 72 to ~37 mN/m. It also has critical micelle concentration of ~28 mg l(-1). Thus, the results presented in our reports show that the produced rhamnolipid can find wide applications in various bioremediation activities such as enhanced oil recovery and petroleum degradation.

In the present study, laboratory scale bioremediation of dual purpose kerosene (DPK) hydrocarbon polluted soil using bulking agent (saw dust) was carried out. The effect of different parameters such as total petroleum hydrocarbon (TPH), dehydrogenase activity (DHase) and pH on bioremediation performance were evaluated. Studied parameters such as microbial dynamics, percentage degradation (95.20%), DHase (8.20 ± 0.43) were found to be higher in saw dust amended system and significantly differed with control at p