Polyaromatic hydrocarbons (PAHs). Handbook on Biodegradation and Biological Treatment of Hazardous Organic Compounds. Dordrecht: Springer Netherlands; 1998. pp. 287-349. [DOI: 10.1007/978-94-015-9062-4_5]

Analysis of a novel strain Brevundimonas KX-1 capable of degrading 3-chlorocarbazole based on the whole genome sequence

In this study, a strain was isolated from a sewage treatment plant in Jiangsu Province, China. The strain was identified as Brevundimonas sp. KX-1. After 5 days, 50.2% 3-chlorocarbazole (3-CCZ) was degraded under the optimum condition as follows: 1 g/L starch, 30 °C, pH 6.5 and 50 mg/L 3-CCZ. The degradation of 3-CCZ by KX-1 conformed to the first-order kinetic model under different initial concentrations in this experiment. The intermediate product of 3-CCZ degradation was identified as (2E,4Z)-6-(2-amino-5-chlorophenyl)-2-hydroxy-6-oxohexa-2,4-dienoic acid. The activities of the meta-cleavage enzymes for biphenyl-2,3-diol (the analogs of intermediate product 2'-amino-5'-chloro-[1,1'-biphenyl]-2,3-diol) were measured with the crude extracts of cells grown in the presence of 3-CCZ. The complete genome of KX-1 was sequenced and compared with the Brevundimonas diminuta BZC3. BZC3 and KX-1 belonged to the same species, displaying the genetic similarity of 99%. But BZC3 could efficiently degrade gentamicin for the potential microbial function analysis. Compared with BZC3, KX-1 possessed the primary function annotations about transportation and metabolism of amino acids (6.65%) and the transportation and metabolism of carbohydrates (5.96%). In addition, KX-1 was rich in sucrose and starch metabolism pathways (ko00500) compared with the genome of BZC3, indicating the high efficiency of KX-1 for starch utilization during degradation. This article reveals the difference between strain KX-1 and bacteria of the same genus in terms of the whole genome sequence, demonstrating that KX-1 is a novel strain Brevundimonas with the ability to degrade 3-CCZ.

PAHs balance in solid and liquid phase of sewage sludge during fermentation process

The results of the quantitative and qualitative analysis of PAHs both in sewage sludge and in supernatants before, during, and after methane fermentation process are presented in this paper. The investigations were carried out under laboratory scale in two series. The sludge samples originated from a municipal treatment plant. The process of fermentation was conducted using batch tests (a one-off batch supplemented with sludges). The content of 16 PAHs, listed by the US EPA, was determined using GC-MS technique. The aim of this investigation was to study changes in contribution groups of hydrocarbons (2-, 3-, 4-, 5-, and 6-ring) in relation to total concentration in PAHs. The objective of these investigations was to follow the changes in the PAHs content not only in sewage sludge (drymass) but also in supernatants (in the liquid phase), and to follow changes in concentration of PAHs during the methane fermentation process as well. The balance of PAHs load in sewage sludge and supernatants mixture was also calculated. An approximate two-fold decrease in dry matter of sludge was observed during the methane fermentation process. During sewage sludge digestion process 3- and 4-ring compounds were released from a solid phase to supernatants.

Rhizoremediation: a beneficial plant-microbe interaction

Worldwide, contamination of soil and ground water is a severe problem. The negative effects of pollutants on the environment and on human health are diverse and depend on the nature of the pollution. The search for alternative methods for excavation and incineration to clean polluted sites resulted in the application of bioremediation techniques. In this review, we describe some generally accepted bioremediation tools and subsequently focus on the combination of two approaches, phytoremediation and bioaugmentation, resulting in rhizoremediation. During rhizoremediation, exudates derived from the plant can help to stimulate the survival and action of bacteria, which subsequently results in a more efficient degradation of pollutants. The root system of plants can help to spread bacteria through soil and help to penetrate otherwise impermeable soil layers. The inoculation of pollutant-degrading bacteria on plant seed can be an important additive to improve the efficiency of phytoremediation or bioaugmentation.