Bioremediating silty soil contaminated by phenanthrene, pyrene, benz(a)anthracene, benzo(a)pyrene using Bacillus sp. and Pseudomonas sp.: Biosurfactant/Beta vulgaris agrowaste effects

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant contaminants which are routinely found in numerous environmental matrices, contributing to ecological degradation. In this study, the removal of LMW and HMW PAHs with 4- and 5 benzene rings, by Bacillus licheniformis STK 01, Bacillus subtilis STK 02 and Pseudomonas aeruginosa STK 03, was evaluated in silty soil for a period of 60 days. Subsequently, a biosurfactant produced from Beta vulgaris agrowaste was used to augment the removal of the aforementioned PAHs in mono- and co cultures. The isolates proved to be proficient in removing the contaminants, with B. licheniformis STK01 cultures achieving the highest removal rates. Biosurfactant supplementation significantly enhanced the removal of benzo(a)pyrene- a 5-ring benzene HMW PAH. The highest removal rates achieved in biosurfactant supplemented cultures were: 100% for phenanthrene, 95.32% for pyrene, 82.71% for benz(a)anthracene and 86.17% for benzo(a)pyrene. The kinetic data used to simulate removal rates were suitably described by first-order kinetics, with the rate constants showing that phenanthrene removal was rapid in cultures without biosurfactant (k = 0.0620 day-1) as well as with biosurfactant (k = 0.0664 day-1), while the removal rates for others followed in the order of their increasing molecular weight. The synergy of the bacterial isolates and the biosurfactant produced from B. vulgaris agrowaste could be used in environmental bioremediation of PAHs even in silty soil.Keywords: Benz(a)anthracene, benzo(a)pyrene, bioremediation, biosurfactant, Beta vulgaris, polycyclic aromatic hydrocarbon

Kinetic modeling of cell growth, substrate utilization, and biosurfactant production from solid agrowaste (Beta vulgaris) by Bacillus licheniformis STK 01

The kinetics of cell growth, substrate utilization and biosurfactant production by Bacillus licheniformis STK 01 from a solid agrowaste substrate (Beta vulgaris) and a refined substrate (mineral salts, MS) was investigated. Data obtained were fitted to the integrated Monod equation, logistic models, and Leudeking–Piret model using nonlinear regression analyses. The maximum cell growth was observed after 72 h of fermentation for both substrates. The highest biosurfactant production was 5.8 ± 0.5 g/L when the B. vulgaris waste substrate was used, while the production increased up to 9.78 ± 1.02 g/L when MS was used. The biosurfactant produced from B. vulgaris and MS lowered the surface tension of the broth to 30 and 23.5 mN/m respectively. Furthermore, from the kinetic data analyses, cell growth and B. vulgaris utilization were described by the logistic model and modified Monod equation, respectively, with the maximum cell growth rate of 0.026 h−1, cell yield of 0.617, and the Monod saturation constant being 0.418 g/L. Similarly, biosurfactant production was best described by the logistic model while the production rate constant was 0.140 h−1. This study is applicable, among other areas, in the design of biological systems augmented with B. vulgaris waste.Cape Peninsula Universityof Technology through the University Research Fund (URF

Bioremediating silty soil contaminated by phenanthrene, pyrene, benz(a)anthracene, benzo(a)pyrene using Bacillus sp. and Pseudomonas sp.: Biosurfactant/Beta vulgaris agrowaste effects

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant contaminants which are routinely found in numerous environmental matrices, contributing to ecological degradation. In this study, the removal of LMW and HMW PAHs with 4- and 5-benzene rings, by Bacillus licheniformis STK 01, Bacillus subtilis STK 02 and Pseudomonas aeruginosa STK 03, was evaluated in silty soil for a period of 60 days. Subsequently, a biosurfactant produced from Beta vulgaris agrowaste was used to augment the removal of the aforementioned PAHs in mono- and co-cultures. The isolates proved to be proficient in removing the contaminants, with B. licheniformis STK01 cultures achieving the highest removal rates. Biosurfactant supplementation significantly enhanced the removal of benzo(a)pyrene- a 5-ring benzene HMW PAH. The highest removal rates achieved in biosurfactant-supplemented cultures were: 100% for phenanthrene, 95.32% for pyrene, 82.71% for benz(a)anthracene and 86.17% for benzo(a)pyrene. The kinetic data used to simulate removal rates were suitably described by first-order kinetics, with the rate constants showing that phenanthrene removal was rapid in cultures without biosurfactant (k = 0.0620 day-1) as well as with biosurfactant (k = 0.0664 day-1), while the removal rates for others followed in the order of their increasing molecular weight. The synergy of the bacterial isolates and the biosurfactant produced from B. vulgaris agrowaste could be used in environmental bioremediation of PAHs even in silty soil

Emulsification of hydrocabons by biosurfactant: exclusive use of agrowwaste

Novel biosurfactant-producing strains were isolated from hydrocarbon-contaminated environments that exclusively utilize agro-waste as their primary carbon source for the expression of biosurfactants. These were quantified using various standardized methods. Among the agro-waste screened, Beta vulgaris (Beetroot) proved to be the most suitable substrate, for which the biosurfactants produced by three bacterial isolates–B. licheniformis STK01, B. subtilis STK02, and P. aeruginosa STK03–lowered the surface tension of the culture media to 30.0, 32.98, and 30.37 mN/m, respectively. The biosurfactants achieved considerable emulsification activity, particularly for heavy hydrocarbons, with the highest emulsification indices being 65.5% and 95% for anthracene and lubricant oil, respectively. The emulsion formed with lubricant oil was thermally stable even up to 50 °C for 21 days. The results showed the proficiency of the novel bacterial isolates used, as well as the suitability of solid agro-waste for biosurfactant production, thus suggesting that exclusive utilization of solid agro-waste is a promising option for use in biosurfactant production for environmental remediation. The outstanding emulsification activity and thermal stability demonstrated by the biosurfactants produced showed their potential applications in enhancing bioavailability and bioremediation of recalcitrant and hydrophobic environmental contaminants

Optimization of surface tension of biosurfactant produced by Bacillus licheniformis STK 01 grown exclusively on beta vugaris using response surface methodology

CPUT Postgraduate Research Conferenc

Isolation of biosurfactant producing strains for enhanced bioremediation of hydrocarbon contaminants

4th World Congress on Biotechnolog

4th World Congress on Biotechnology,

4th World Congress on Biotechnology September 23-25, 2013 DoubleTree by Hilton Hotel Raleigh-Durham Airport at RTP, NC, USABiosurfactants are surface active agents produced by microorganisms. Due to their amphiphilic structure, biosurfactants show a wide range of properties, including the lowering of surface and interfacial tension of liquids, the ability to form micelles and microemulsions between two different phases, the ability to increase the surface area of hydrophobic water-insoluble substances, and thus increase the water bioavailability of such substances. The present study focused on the isolation of novel biosurfactant producing strains from hard surfaces (tar surfaces) which exclusively utilize agrowaste as their primary carbon source for the expression of the biosurfactants – quantified using various standardized methods. Agrowastes used were; Pear (P, Pyrus), Pineapple (PP, Ananas comosus), Apple (A, Malus domestica), Beetroot (B, Beta vulgaris), Brewers spent yeast (SPY), PP plus SPY, B plus SPY, P plus SPY, PP plus SPY and A plus SPY. The drop-collapse method showed that the highest biosurfactant production was achieved using B. vulgaris. Surface tension reduction and emulsification index were used to screen the biosurfactant produced for its potential application in enhancing bioavailability of hydrocarbon contaminants. Emulsification was carried out using diesel, engine oil, cyclohexane, phenanthrene and benz(a)anthracene as hydrocarbons. The biosurfactant produced using B. vulgaris waste as a sole carbon source (without supplementation with refined carbohydrates, inducers, etc.) was able to lower the surface tension of the medium to 33 mN/m within 4 days of incubation without optimization – for which the crude extract formed stable emulsions. The results obtained in this study demonstrated the feasibility of producing biosurfactants using renewable and easily available resources as sole and primary carbon sources. The emulsification achieved showed the biosurfactants’ propensity for use in enhancing bioavailability and hence, bioremediation of an environment contaminated with various hydrocarbons

Environmental Biotechnology – New Approaches and Prospective Applications

Petre M (ed): Environmental Biotechnology – New Approaches and Prospective Applications Rijeka, Croatia: InTech Online Publishers, 2013, pp 171-194, ISBN 978-953-51-0972-3Polycyclic aromatic hydrocarbons (PAHs) are the world’s largest class of carcinogens known to date, not only because of their ability to cause gene mutation and cancer, but due to their persistency in the environment. They are particularly recalcitrant due to their molecular weight, hydrophobic nature and thus, accumulate in various matrices in the environment. PAHs, also known as polyarenes or polynuclear aromatic hydrocarbons, are formed and released into the environment through natural and anthropogenic sources. Natural sources include volcanoes and forest fires while anthropogenic sources include, majorly, incomplete combustion of fossil fuels, wood burning, municipal and industrial waste incineration. PAHs containing two or three fused benzene rings are classified as low molecular weight (LMW) PAHs and are more water soluble while those with four or more benzene rings are referred to as high molecular weight (HMW) PAHs. They tend to adsorb onto soil and sediment thus, making them recalcitrant in the environment. Sixteen of these organic compounds have been identified as priority pollutants due to their hazardous properties, with HMW PAHs being considered as potential human carcinogens, by the United State Environmental Protection Agency [1]

Free cyanide and thiocyanate biodegradation by Pseudomonas aeruginosa STK 03 capable of heterotrophic nitrification under alkaline conditions

An alkali-tolerant bacterium, Pseudomonas aeruginosa STK 03 (accession number KR011154), isolated from an oil spill site, was evaluated for the biodegradation of free cyanide and thiocyanate under alkaline conditions. The organism had a free cyanide degradation efficiency of 80 and 32 % from an initial concentration of 250 and 450 mg CN−/L, respectively. Additionally, the organism was able to degrade thiocyanate, achieving a degradation efficiency of 78 and 98 % from non- and free cyanide spiked cultures, respectively. The organism was capable of heterotrophic nitrification but was unable to denitrify aerobically. The organism was unable to degrade free cyanide in the absence of a carbon source, but it was able to degrade thiocyanate heterotrophically, achieving a degradation efficiency of 79 % from an initial concentration of 250 mg SCN−/L. Further increases in thiocyanate degradation efficiency were only observed when the cultures were spiked with free cyanide (50 mg CN−/L), achieving a degradation efficiency of 98 % from an initial concentration of 250 mg SCN−/L. This is the first study to report free cyanide and thiocyanate degradation by Pseudomonas aeruginosa. The higher free cyanide and thiocyanate tolerance of the isolate STK 03, which surpasses the stipulated tolerance threshold of 200 mg CN−/L for most organisms, could be valuable in microbial consortia for the degradation of cyanides in an industrial setting.Cape Peninsula University of Technology (CPUT), University Research Fund (URF RK 16) and National Research Foundation (NRF)