The effect of Pb + Zn on coelomocyte riboflavin content in the epigeic earthworm Dendrodrilus rubidus inhabiting three metalliferous soils and one reference soil was measured by flow cytometry and spectrofluorimetry. A reciprocal polluted <-> unpolluted worm transfer experiment (4-week exposure) was also performed. High proportions of autofluorescent eleocytes were counted in worms from all localities, but intense riboflavin-derived autofluorescence was detectable only in reference worm eleocytes. Other findings were: (i) fluorophore(s) other than riboflavin is/are responsible for eleocyte autofluorescence in residents of metalliferous soils; (ii) riboflavin content was reduced in the eleocytes of worms transferred from unpolluted to metal-polluted soil; (iii) the riboflavin content of D. rubidus eleocytes is a promising biomarker of exposure; (iv) COII mitochondrial genotyping revealed that the reference population is genetically distinct from the three mine populations; (v) metal exposure rather than genotype is probably the main determinant of inter-population differences in eleocyte riboflavin status. Soil metal pollution reduces riboflavin content of earthworm eleocytes.

Anaerobic fermentation of waste activated sludge (WAS) for recycling valuable volatile fatty acids (VFAs) is economically valuable. However, the fermentation of protein is the rate-limiting step of VFA production with WAS as a substrate. In this study, the effect of redox mediators (RMs, i.e., riboflavin and lawsone) on the enhanced production of VFAs from WAS was investigated. The results indicate that both RMs can promote protein-dependent fermentation, increasing maximum VFA accumulation by 43.9% and 42.5% respectively. In cultures supplemented with riboflavin and lawsone, VFA production was highly correlated with protease activities, but not with α-glucosidase activities. This implies that RMs affected the redox reaction of amino acids degradation, resulting in an increased release of ammonia. Sequencing results showed that RMs significantly increased the abundance of bacteria related to VFA fermentation and protein/amino acid degradation at the levels of phylum, class, order, family, and even genus.

A serial enrichment culture has been grown in an alkaline Fe(III)-citrate-containing medium from an initial inoculum from a soil layer beneath a chromium ore processing residue (COPR) disposal site where Cr(III) is accumulating from Cr(VI) containing leachate. This culture is dominated by two bacterial genera in the order Clostridiales, Tissierella, and an unnamed Clostridium XI subgroup. This paper investigates the growth characteristics of the culture when Cr(VI) is added to the growth medium and when aquifer sand is substituted for Fe(III)-citrate. The aim is to determine how the availability and chemical form of Fe(III) affects the growth of the bacterial consortium, to determine the impact of Cr(VI) on growth, and thus attempt to understand the factors that are controlling Cr(III) accumulation beneath the COPR site. The culture can grow fermentatively at pH 9.2, but growth is stronger when it is associated with Fe(III) reduction. It can withstand Cr(VI) in the medium, but growth only occurs once Cr(VI) is removed from solution. Cr(VI) reduced the abundance of Tissierella sp. in the culture, whereas the Clostridium XI sp. was Cr(VI) tolerant. In contrast, growth with solid phase Fe(III)-oxyhydroxides (present as coatings on aquifer sand) favoured the Tissierella C sp., possibly because it produces riboflavin as an extracellular electron shuttling compound allowing more efficient electron transfer to solid Fe(III) phases. Thus, it is suggested that bacterially mediated Cr(III) reduction in the soil beneath the COPR site is dependent on Fe(III) reduction to sustain the bacterial community.

The photodegradation processes of fenpropathrin and λ-cyhalothrin were studied in hexane, methanol/water (1:1, v/v), and acetone in both ultraviolet light and simulated sunlight. Intermediates in the photodegradation process were identified using gas chromatography/mass spectrometry (GC/MS), and the analysis of intermediates was used to speculate on possible photodegradation pathways. The photodegradation processes of fenpropathrin and λ-cyhalothrin followed pseudo first-order kinetics. The photodegradation rates varied according to the solvent in decreasing order: hexane > methanol/water (1:1, v/v) > acetone. The effects of substances coexisting in the environment on the photodegradation of pyrethroids were also investigated in the research. Acetone, humic acid, and riboflavin increased photodegradation rates while L-ascorbic acid slowed the process. This study provides a theoretical basis for the removal of pyrethroid pollution from the natural environment.

The superoxide anion radical (O₂•⁻) is one of the most predominant reactive oxygen species (ROS), which is also involved in diverse chemical and biological processes. In this study, O₂•⁻ was generated by irradiating riboflavin in an O₂-saturated solution using an ultraviolet lamp (λₑₘ = 365 nm) as the light source. The photochemical reduction of 1,4-benzoquinone (p-BQ) by O₂•⁻ was explored by 355-nm laser flash photolysis (LFP) and 365-nm UV light steady irradiation. The results showed that the photodecomposition efficiency of p-BQ was influenced by the riboflavin concentration, p-BQ initial concentration, and pH values. The superoxide anion radical originating from riboflavin photolysis served as a reductant to react with p-BQ, forming reduced BQ radicals (BQ•⁻) with a second-order rate constant of 1.1 × 10⁹ L mol⁻¹ s⁻¹. The main product of the photochemical reaction between p-BQ and O₂•⁻ was hydroquinone (H₂Q). The present work suggests that the reaction with O₂•⁻ is a potential transformation pathway of 1, 4-benzoquinone in atmospheric aqueous environments.

Vermicomposting is an eco-friendly technology, where earthworms are introduced in the waste, inter alia sewage sludge, to cooperate with microorganisms and enhance decomposition of organic matter. The main aims of the present study was to determine the influence of two different earthworm species, Eisenia fetida and Eisenia andrei, on the changes of selected metallic trace elements content in substratum during vermicomposting process using three different sewage sludge mainly differentiated by their metal contents. Final vermicompost has shown a slight reduction in Cd, Cu, Ni, and Pb, while the Zn concentration tends to increase. Accumulation of particular heavy metals in earthworms’ bodies was assessed. Both species revealed high tendency to accumulate Cd and Zn, but not Cu, Ni, and Pb, but E. andrei has higher capabilities to accumulate some metals. Riboflavin content, which content varies depending on metal pollution in several earthworms species, was measured supravitaly in extruded coelomocytes. Riboflavin content decreased slightly during the first 6 weeks of exposure and subsequently restored till the end of the 9-week experiment. Selected agronomic parameters have also been measured in the final product (vermicompost) to assess the influence of earthworms on substratum.

Biofouling material samples from the Arabian (Persian) Gulf, used as inocula in batch cultures, brought about crude oil and pure-hydrocarbon removal in a mineral medium. Without any added nitrogen fertilizers, the hydrocarbon-removal values were between about 10 and 50 %. Fertilization with NaNO₃alone or together with a mixture of the vitamins thiamine, pyridoxine, vitamin B12, biotin, riboflavin, and folic acid increased the hydrocarbon-removal values, to reach 90 %. Biofouling material samples harbored total bacteria in the magnitude of 10⁷cells g⁻¹, about 25 % of which were hydrocarbonoclastic. These numbers were enhanced by NaNO₃and vitamin amendment. The culture-independent analysis of the total bacterioflora revealed the predominance of the gammaproteobacterial genera Marinobacter, Acinetobacter, and Alcanivorax, the Flavobacteriia, Flavobacterium, Gaetbulibacter, and Owenweeksia, and the Alphaproteobacteria Tistrella, Zavarzinia, and others. Most of those bacteria are hydrocarbonoclastic. Culture-dependent analysis of hydrocarbonoclastic bacteria revealed that Marinobacter hydrocarbonoclasticus, Dietzia maris, and Gordonia bronchialis predominated in the fouling materials. In addition, each material had several more-specific hydrocarbonoclastic species, whose frequencies were enhanced by NaNO₃and vitamin fertilization. The same samples of fouling materials were used in four successive crude-oil-removal cycles without any dramatic loss of their hydrocarbon-removal potential nor of their associated hydrocarbonoclastic bacteria. In the fifth cycle, the oil-removal value was reduced by about 50 % in only one of the studied samples. This highlights how firmly biofouling materials were immobilizing the hydrocarbonoclastic bacteria.