Isolation and application of Gordonia sp. JC11 for removal of boat lubricants

Boat lubricants are continuously released into the marine environment and thereby cause chronic oil pollution. This study aims to isolate lubricant-degrading microorganisms from Thai coastal areas as well as to apply a selected strain for removal of boat lubricants. Ten microorganisms in the genera of Gordonia, Microbacterium, Acinetobacter, Pseudomonas, Brucella, Enterococcus and Candida were initially isolated by crude oil enrichment culture techniques. The lubricant-removal activity of these isolates was investigated with mineral-based lubricants that had been manufactured for the 4-stroke diesel engines of fishing boats. Gordonia sp. JC11, the most effective strain was able to degrade 25-55% of 1,000 mg L(-1) total hydrocarbons in six tested lubricants, while only 0-15% of the lubricants was abiotically removed. The bacterium had many characteristics that promoted lubricant degradation such as hydrocarbon utilization ability, emulsification activity and cell surface hydrophobicity. For bioaugmentation treatment of lubricant contaminated seawater, the inoculum of Gordonia sp. JC11 was prepared by immobilizing the bacterium on polyurethane foam (PUF). PUF-immobilized Gordonia sp. JC11 was able to remove 42-56% of 100-1,000 mg L(-1) waste lubricant No. 2 within 5 days. This lubricant removal efficiency was higher than those of free cells and PUF without bacterial cells. The bioaugmentation treatment significantly increased the number of lubricant-degrading microorganisms in the fishery port seawater microcosm and resulted in rapid removal of waste lubricant No. 2.     

Bioremediation of polychlorinated biphenyl-contaminated soil using carvone and surfactant-grown bacteria

Partial bioremediation of polychlorinated biphenyl (PCB)-contaminated soil was achieved by repeated applications of PCB-degrading bacteria and a surfactant applied 34 times over an 18-week period. Two bacterial species, Arthrobacter sp. strain B1B and Ralstonia eutrophus H850, were induced for PCB degradation by carvone and salicylic acid, respectively, and were complementary for the removal of different PCB congeners. A variety of application strategies was examined utilizing a surfactant, sorbitan trioleate, which served both as a carbon substrate for the inoculum and as a detergent for the mobilization of PCBs. In soil containing 100 μg Aroclor 1242 g⁻¹ soil, bioaugmentation resulted in 55–59% PCB removal after 34 applications. However, most PCB removal occurred within the first 9 weeks. In contrast, repeated addition of surfactant and carvone to non-inoculated soil resulted in 30–36% PCB removal by the indigenous soil bacteria. The results suggest that bioaugmentation with surfactant-grown, carvone-induced, PCB-degrading bacteria may provide an effective treatment for partial decontamination of PCB-contaminated soils. Received: 9 March 2000 / Received revision: 27 June 2000 / Accepted: 16 July 2000     

Cometabolism of trichloroethylene: concepts, limitations and available strategies for sustained biodegradation

Due to its toxicity and persistence in the environment, trichloroethylene (TCE) has become a major soil and groundwater contaminant in many countries. A group of aliphatic- and aromatic-degrading bacteria expressing nonspecific oxygenases have been reported to transform TCE through aerobic cometabolism in the presence of primary substrate such as methane, ammonia, propane, phenol, toluene or cumene. This paper reviews the fundamentals and results of TCE cometabolism from laboratory and field studies. The limitations associated with TCE cometabolism including the causes and effects of substrate and/or inducer utilization rate and depletion, enzyme inhibition and inactivation, and cytotoxicity during TCE oxidation among various TCE-degrading bacteria and enzymes are discussed. In addition, the potential strategies e.g. addition of primary substrate/inducer or external energy substrate, use of a two-stage reactor and application of cell immobilization for sustained TCE degradation are highlighted. The review summarizes important information on TCE cometabolism, which is necessary for developing efficient TCE bioremediation approaches.     

Silica-immobilized Methylobacterium sp. NP3 and Acinetobacter sp. PK1 degrade high concentrations of phenol

Aims: To immobilize Methylobacterium sp. NP3 and Acinetobacter sp. PK1 to silica and determine the ability of the immobilized bacteria to degrade high concentrations of phenol. Methods and Results: The phenol degradation activity of suspended and immobilized Methylobacterium sp. NP3 and Acinetobacter sp. PK1 bacteria was investigated in batch experiments with various concentrations of phenol. The bacterial cells were immobilized by attachment to or encapsulation in silica. The encapsulated bacteria had the highest phenol degradation rate, especially at initial phenol concentrations between 7500 and 10 000 mg l^?1. Additionally, the immobilized cells could continuously degrade phenol for up to 55 days. Conclusions: The encapsulation of a mixed culture of Methylobacterium sp. NP3 and Acinetobacter sp. PK1 is an effective and easy technique that can be used to improve bacterial stability and phenol degradation. Significance and Impact of the Study: Wastewater from various industries contains high concentrations of phenol, which can cause wastewater treatment failure. Silica‐immobilized bacteria could be applied in bioreactors to initially remove the phenol, thereby preventing phenol shock loads to the wastewater treatment system.     

Degradation of phenanthrene on plant leaves by phyllosphere bacteria

The activity of phyllosphere bacteria in the degradation of phenanthrene was investigated as a mechanism for the removal of atmospheric phenanthrene after its deposition on plant leaves. Initially, leaf samples of six plant species were collected from two roadsides in Bangkok to determine the presence of phenanthrene-degrading bacteria. The numbers of phenanthrene-degrading phyllosphere bacteria were varied and ranged from 3.5 x 10(4) to 1.95 x 10(7) CFU/g, in which the highest number was found from Ixora sp. Further studies were carried out in the laboratory by spraying phenanthrene on Ixora sp. leaves and then monitoring the amount of deposited phenanthrene and number of phenanthrene-degrading bacteria after incubation. The results showed that the amount of phenanthrene was significantly reduced on leaves containing phenanthrene-degrading bacteria. These were detected along with a rapid increase in the number of bacteria on leaves. The results indicated that many phyllosphere bacteria could utilize phenanthrene to support their growth and thereby reduce the amount of deposited phenanthrene on leaf surfaces. Several phenanthrene-degrading bacteria were later isolated from the leaves and identified with a high 16S rDNA sequence similarity to the genera Pseudomonas, Microbacterium, Rhizobium, and Deinococcus.     

Cometabolic Degradation of Trichloroethene by Rhodococcus sp. Strain L4 Immobilized on Plant Materials Rich in Essential Oils

The cometabolic degradation of trichloroethene (TCE) by Rhodococcus sp. L4 was limited by the loss of enzyme activity during TCE transformation. This problem was overcome by repeated addition of inducing substrates, such as cumene, limonene, or cumin aldehyde, to the cells. Alternatively, Rhodococcus sp. L4 was immobilized on plant materials which contain those inducers in their essential oils. Cumin seeds were the most suitable immobilizing material, and the immobilized cells tolerated up to 68 μM TCE and degraded TCE continuously. The activity of immobilized cells, which had been inactivated partially during TCE degradation, could be reactivated by incubation in mineral salts medium without TCE. These findings demonstrate that immobilization of Rhodococcus sp. L4 on plant materials rich in essential oils is a promising method for efficient cometabolic degradation of TCE.Various bacteria have been reported to degrade trichloroethene (TCE) aerobically via cometabolic degradation with broad-substrate-specificity enzymes (2). However, TCE cometabolic degradation is considered an unsustainable process due to cytotoxicity, inhibition, or inactivation of TCE-degrading enzymes. These phenomena have been observed in studies using both whole cells and purified enzymes, including soluble methane monooxygenases from Methylosinus trichosporium OB3b (9) and Nitrosomonas europaea (13), toluene 2-monooxygenase from Burkholderia cepacia G4 (19, 27), toluene dioxygenase (TDO) from Pseudomonas putida F1 (15, 18), and butane-oxidizing bacteria, i.e., Pseudomonas butanovora, Mycobacterium vaccae, and Nocardioides sp. CF8 (11). Nevertheless, the addition of an inducer or growth substrate can maintain TCE cometabolic degradation. For example, the TCE-degrading activity of P. putida F1 toluene dioxygenase was restored after adding benzene, cumene, or toluene to displace TCE and its reactive intermediates from the enzyme active site (18). Arp et al. (2) suggested that the rate of enzyme maintenance and recovery depended on the extent of inactivation and the balance of TCE and inducer/growth substrate concentrations.Plant essential oils and their components, such as citral, limonene, cumene, and cumin aldehyde, have been found to induce TCE degradation in Rhodococcus sp. L4 (24). However, the removal of TCE by this bacterium was effective only for a short period. The impacts of TCE on Rhodococcus spp. and their enzymes have not been studied in detail, even though many bacteria of this genus exhibited high TCE-degrading activities (i.e., Rhodococcus erythropolis JE 77, R. erythropolis BD2, Rhodococcus sp. Sm-1, and Rhodococcus sp. Wrink) (5, 6, 7, 16). This study therefore investigated the changes in TCE-degrading activity of Rhodococcus sp. L4 cells and TDO during exposure to TCE. Two enzyme maintenance approaches were evaluated, namely, repeated addition of essential oil components to the system and immobilization of the bacterial cells on plant material rich in essential oils. Immobilized microorganisms are generally capable of degrading pollutants at a higher initial concentration and for a longer period than those of free cells (21, 23), possibly because the microbial cells are protected from environmental stress and toxic compounds (3). In this study, the plant materials were used to provide a solid surface for bacterial attachment and a continuous source of essential oils for inducing TCE-degrading enzymes. Our results show that the repeated addition of limonene, cumene, or cumin aldehyde enhances TCE degradation and that bacteria immobilized on cumin seeds are able to maintain their TCE-degrading activity.     

Natural Attenuation, Biostimulation, and Bioaugmentation in 4-Chloroaniline-Contaminated Soil

Bioremediation treatments including natural attenuation (NA), biostimulation (BS), and bioaugmentation (BA) were performed and compared regarding the degradation of 4-chloroaniline (4CA) contaminating two types of agricultural soil collected from Nakornnayok (NN) and Chiangmai (CM) provinces, Thailand. Despite the different soil properties, both soil types exhibited intrinsic potential for biodegradation. 4CA degradation by NA in loam soil-NN was fairly effective (ca. 40%), while in sandy-clay loam soil-CM it occurred poorly (<10%). Compared to NA, BS with aniline and BA with 4CA-degrading Klebseilla sp. CA17 were comparatively more effective techniques, although the degradation occurred differently in each soil type. In soil-NN, the biodegradation of 4CA took place at a higher rate, achieving biodegradation of 70–75% within 4 weeks, than in soil-CM, i.e., up to 40–46% within 8 weeks. During each treatment, changes in soil microbial activity, numbers of 4CA-degrading micro-organisms, and dynamic modification of soil microbial community structure were also monitored. The results suggest that both BS and BA are feasible techniques for bioremediation of 4CA accumulated in soil, although the biodegrading efficiency in soil environment depends not only on site characteristics but also on the characteristics of either indigenous microbial population or the survival and stability of bioaugmented cultures.     

Trichloroethylene cometabolic degradation by Rhodococcus sp. L4 induced with plant essential oils

Cometabolic degradation of TCE by toluene-degrading bacteria has the potential for being a cost-effective bioremediation technology. However, the application of toluene may pose environmental problems. In this study, several plant essential oils and their components were examined as alternative inducer for TCE cometabolic degradation in a toluene-degrading bacterium, Rhodococcus sp. L4. Using the initial TCE concentration of 80 muM, lemon and lemongrass oil-grown cells were capable of 20 +/- 6% and 27 +/- 8% TCE degradation, which were lower than that of toluene-grown cells (57 +/- 5%). The ability of TCE degradation increased to 36 +/- 6% when the bacterium was induced with cumin oil. The induction of TCE-degrading enzymes was suggested to be due to the presence of citral, cumin aldehyde, cumene, and limonene in these essential oils. In particular, the efficiency of cumin aldehyde and cumene as inducers for TCE cometabolic degradation was similar to toluene. TCE transformation capacities (T (c)) for these induced cells were between 9.4 and 15.1 mug of TCE mg cells(-1), which were similar to the known toluene, phenol, propane or ammonia degraders. Since these plant essential oils are abundant and considered non-toxic to humans, they may be applied to stimulate TCE degradation in the environment.     

Contents Volume 12

Volume Contents

Contents Volume 12