Effect of rhamnolipids on microbial biomass content and biochemical parameters in soil contaminated with coal tar creosote

Abstract

The objective of the present study was to compare the effect of rhamnolipids on the microbial biomass content and the activity of dehydrogenases (DHA), acid phosphatase (ACP), alkaline phosphatase (ALP), and urease (URE) in soil contaminated with two types of coal tar creosote: type C and type GX-Plus. The experiment was carried out on samples of sandy clay loam under laboratory conditions. Coal tar creosote was added to soil samples at a dose of 0 and 10 g·kg−1 DM, along with rhamnolipids at a dose of 0, 10, 100, and 1000 mg·kg−1 DM. The humidity of the samples was brought to 60% maximum water holding capacity, and the samples were incubated at 20°C. Microbial and biochemical parameters were determined on days 1, 7, 21, and 63. The obtained results demonstrated that the addition of rhamnolipids did not result in any significant changes in the activity of the determined parameters in the uncontaminated soil. However, it was observed that the application of these biosurfactants, particularly at the dose of 1000 mg·kg−1 DM, largely decreased the effect of coal tar creosote on the determined parameters. Moreover, the microbial biomass and the activity of ALP and URE were found to be the best indicator of bioremediation of soil contaminated with coal tar creosote.

Analysis of Chemical and Biochemical Parameters of Petrol-Contaminated Soil after Biostimulation with an Enzyme Reagent

“…Moreover, the chemical composition and other environmental factors such as pH and temperature have an influence on the biodegradation process and enzymatic activity. The decrease in enzyme activity observed in the initial period of the experiment, especially DHA, may result from disturbances in soil air conditions [39]. It is also worth noting the quantitative and qualitative composition of indigenous microflora.…”

“…Contamination of the soil with light crude oil fractions mainly stimulated the activity of oxidoreductases [3], but inhibited the activity of hydrolases [37], which was also confirmed by the results of the present study. On the other hand, the introduction of heavier crude oil fractions such as diesel oil, spent engine oil, or coal tar creosote into the soil negatively impacted the activity of all soil enzymes [9,17,31,38,39]. An analysis of the effect of Fyre-Zyme preparation (IF FZ ) on DHA in the uncontaminated and petrol contaminated soil, based on the values of the enzyme coefficients, indicated that the values were close to 1, on all measurement dates, for each type of preparation application.…”

“…The results of the studies carried out so far on the influence of various additives on biochemical processes in the soil are also inconclusive. Both increases and decreases in degradation processes as a result of the introduction of biopreparations and different additives have been observed [3,11,22,39,50]. The effectiveness of this treatment is determined by numerous factors of a biological and physicochemical nature [51].…”