Effects of 2,6-di-tert-butyl-hydroxytotulene and mineral-lubricant base oils on microbial communities during lubricants biodegradation

2,6-Di-tert-butyl-hydroxytotulene (BHT) is an additive commonly used in the manufacturing of lubricants to improve their antioxidant properties. However, in this study, we found that BHT affects the biodegradation of bio-lubricants by influencing the microbial community during the degradation of bio-lubricants. Specifically, BHT was found to reduce bacterial richness in activated sludge, but it increased the relative abundance of Actinobacteria (from 21.24% to 40.89%), Rhodococcus (from 17.15% to 31.25%), Dietzia (from 0.069% to 6.49%), and Aequorivita (from 0.90% to 1.85%). LEfSe analysis and co-occurrence network analysis suggested that Actinobacteria could be potential biomarkers and keystone taxa in microbial communities. Using the MetaCyc pathway database, the study found that BHT interfered with cellular biosynthetic processes. Additionally, the study also showed that mineral-lubricant base oils, which are difficult to degrade, significantly altered the diversity and composition of the microbiome. Overall, the findings demonstrate that BHT and mineral-lubricant base oils can substantially alter bacterial richness, structure, and function, potentially contributing to the difficulty in degrading lubricants. These findings have implications for the development of more biodegradable lubricants and the management of industrial waste containing lubricants.

The production of wax esters in transgenic plants: towards a sustainable source of bio-lubricants

Wax esters are high-value compounds used as feedstocks for the production of lubricants, pharmaceuticals, and cosmetics. Currently, they are produced mostly from fossil reserves using chemical synthesis, but this cannot meet increasing demand and has a negative environmental impact. Natural wax esters are also obtained from Simmondsia chinensis (jojoba) but comparably in very low amounts and expensively. Therefore, metabolic engineering of plants, especially of the seed storage lipid metabolism of oil crops, represents an attractive strategy for renewable, sustainable, and environmentally friendly production of wax esters tailored to industrial applications. Utilization of wax ester-synthesizing enzymes with defined specificities and modulation of the acyl-CoA pools by various genetic engineering approaches can lead to obtaining wax esters with desired compositions and properties. However, obtaining high amounts of wax esters is still challenging due to their negative impact on seed germination and yield. In this review, we describe recent progress in establishing non-food-plant platforms for wax ester production and discuss their advantages and limitations as well as future prospects.

Non-edible vegetable oil-based feedstocks capable of bio-lubricant production for automotive sector applications-a review

Fossil fuel resource is on the draining stage which leads to an increment in the cost of the petroleum products. Nowadays, research is focused on the development of environment-friendly lubricants which are derivatives of renewable sources. Bio-lubricants based on non-edible oil sources are environmentally friendly because they are non-hazardous and biodegradable and no emission of toxic gases were detected when they are used. This study involves the characterizations and advantages, as well as utilization of inedible plant oil-driven bio-lubricants as an alternative for tribological applications. This report also presents the status of the global lubricant market as well as the potential outlook of the bio-lubricants for their future usage. Non-edible plant oil-driven bio-lubricants bear high viscosity, high lubricity, and high viscosity index which can enhance the equipment service life and deserve the ability to carry the high load and results in a minimum amount of metal traces during combustion while applied to engines. Beside their advantages, some of the disadvantages are also there which can be addressed by the employment of certain additives available according to the applications. The detailed study about the different additives utilized during their use in the internal combustion engine is also described in detail during this study. This study provides a detailed description of the possibilities associated with bio-lubricant based on non-edible oil feedstocks to the automotive sector applications.

Tuning culturing conditions towards the production of neutral lipids from lubricant-based wastewater in open mixed bacterial communities

Production of bacterial lipid-based biofuels using inexpensive substrates, as wastes, is an emerging approach. In this work, a selective process using carbon feast-famine cycles was applied to obtain an indigenous microbial community of hydrocarbon-degrading and lipid-accumulating bacteria, using a real lubricant-based wastewater as carbon source. In the conditions applied, the enriched bacterial community, dominated by members of the genus Rhodococcus, Pseudomonas and Acinetobacter, was able to degrade almost all hydrocarbons present in the wastewater within 24 h' incubation and to accumulate, although in low levels, triacylglycerol (TAG) (<5% of cell dry weight (CDW)) and polyhydroxyalkanoates (PHA) (3.8% ± 1.1% of the CDW) as well as an unknown lipid (29% ± 6% of CDW), presumably a wax ester-like compound. The influence of culture conditions, namely carbon and nitrogen concentrations (and C/N ratio) and cultivation time, on the amount and profile of produced storage compounds was further assessed using a statistical approach based on a central composite circumscribed design and surface response methodology. The regression analysis of the experimental design revealed that only nitrogen concentration and C/N ratio are significant for neutral lipid biosynthesis (p < 0.05). Maximum neutral lipid content, i.e. 33% (CDW basis), was achieved for the lowest carbon and nitrogen concentrations evaluated (10 g COD L^-1 and 0.02 g N L^-1). PHA accounted for less than 5% of CDW. In these conditions, neutral lipid content was mainly composed by TAG, about 70% (w/w). TAG precursors, namely monoacylglycerols (MAG), diacylglycerols (DAG) and fatty acids (FA), accounted for 22% of total neutral lipids and WE for about 7%. Nevertheless, according to the applied response surface model, further improvement of neutral lipids content is still possible if even lower nitrogen concentrations are used. The fatty acids detected in TAG extracts ranged from myristic acid (C14:0) to linoleic acid (C18:2), being the most abundant palmitic acid (C16:0), stearic acid (C18:0) and oleic acid (C18:1). This study shows the feasibility of combining treatment of hydrocarbon contaminated wastewater, herein demonstrated for lubricant-based wastewater, with the production of bacterial neutral lipids using open mixed bacterial communities. This approach can decrease the costs associated to both processes and contribute to a more sustainable waste management and production of lipid-based biofuels.

Dermal penetration and resorption of beta-naphthylamine and N-phenyl-beta-naphthylamine from lubricants in an ex vivo human skin model

Dermal Penetration of aromatic amines (AA's), often suspected or known to be carcinogenic, can play an important role in the overall human exposure. However, information on penetration of certain AA's is poor and inconsistent. Penetration of the former lubricant additive N-phenyl-beta-naphthylamine (PBNA) and its contaminant beta-naphthylamine (BNA) a known carcinogen was investigated and the influence of formulation and co-application characterized. Percutaneous penetration of BNA and PBNA through freshly excised human skin (n = 8; 48 h) was investigated using an ex vivo diffusion cell model. Both AA's were applied in a technical-conform lubricant or dissolved in hexane. The amount of BNA and PBNA applied to skin was 0.52 and 259 μg/0.64 cm². The analytical determination of AA's was performed by GC-MS. Both, BNA and PBNA penetrated through human skin (38 vs. 5% of applied dose). In contrast to BNA, the percutaneous penetration of PBNA continued beyond the end of exposure. Co-exposure of both AA's increased the intradermal uptake of BNA and PBNA (p < 0.05). Exposure in lubricant showed the least overall penetration (2.9 and 1.9% of applied dose). The results clearly reveal that dermal penetration of both AA's depends strongly on the mode of application. Co-application and formulation alters the penetration of the AA's.

Bioremediation of diesel and lubricant oil-contaminated soils using enhanced landfarming system

Lubricant and diesel oil-polluted sites are difficult to remediate because they have less volatile and biodegradable characteristics. The goal of this research was to evaluate the potential of applying an enhanced landfarming to bioremediate soils polluted by lubricant and diesel. Microcosm study was performed to evaluate the optimal treatment conditions with the addition of different additives (nutrients, addition of activated sludge from oil-refining wastewater facility, compost, TPH-degrading bacteria, and fern chips) to enhance total petroleum hydrocarbon (TPH) removal. To simulate the aerobic landfarming biosystem, air in the microcosm headspace was replaced once a week. Results demonstrate that the additives of activated sludge and compost could result in the increase in soil microbial populations and raise TPH degradation efficiency (up to 83% of TPH removal with 175 days of incubation) with initial (TPH = 4100 mg/kg). The first-order TPH degradation rate reached 0.01 1/d in microcosms with additive of activated sludge (mass ratio of soil to inocula = 50:1). The soil microbial communities were determined by nucleotide sequence analyses and 16S rRNA-based denatured gradient gel electrophoresis. Thirty-four specific TPH-degrading bacteria were detected in microcosm soils. Chromatograph analyses demonstrate that resolved peaks were more biodegradable than unresolved complex mixture. Results indicate that more aggressive remedial measures are required to enhance the TPH biodegradation, which included the increase of (1) microbial population or TPH-degrading bacteria, (2) biodegradable carbon sources, (3) nutrient content, and (4) soil permeability.

Biosurfactant Production by Bacillus salmalaya for Lubricating Oil Solubilization and Biodegradation

This study investigated the capability of a biosurfactant produced by a novel strain of Bacillus salmalaya to enhance the biodegradation rates and bioavailability of organic contaminants. The biosurfactant produced by cultured strain 139SI showed high physicochemical properties and surface activity in the selected medium. The biosurfactant exhibited a high emulsification index and a positive result in the drop collapse test, with the results demonstrating the wetting activity of the biosurfactant and its potential to produce surface-active molecules. Strain 139SI can significantly reduce the surface tension (ST) from 70.5 to 27 mN/m, with a critical micelle concentration of 0.4%. Moreover, lubricating oil at 2% (v/v) was degraded on Day 20 (71.5). Furthermore, the biosurfactant demonstrated high stability at different ranges of salinity, pH, and temperature. Overall, the results indicated the potential use of B. salmalaya 139SI in environmental remediation processes.

Ionic liquids as lubricants or lubrication additives: an ecotoxicity and biodegradability assessment

This paper reports on the (eco)toxicity and biodegradability of ionic liquids considered for application as lubricants or lubrication additives. Ammonium- and pyrrolidinium-based cations combined with methylsulphate, methylsulphonate and/or (CF(3)SO(2))(2)N(-) anions were investigated in tests to determine their aquatic toxicity using water fleas Daphnia magna, green algae Selenastrum capricornutum and marine bacteria (Vibrio fischeri). Additional test systems with an isolated enzyme (acetylcholinesterase) and isolated leukaemia cells from rats (IPC-81) were used to assess the biological activity of the ionic liquids. These compounds generally exhibit low acute toxicity and biological activity. Their biodegradability was screened according to OECD test procedures 301 B and 301 F. For choline and methoxy-choline ionic liquids ready biodegradability was observed within 5 or 10 d, respectively. Some of the compounds selected have a considerable potential to contribute to the development of more sustainable products and processes.

Effects of surfactants on rhizodegradation of oil in a contaminated soil

The effects of nonionic surfactants on degradation of engine oil in metal contaminated soil using Indian mustard (Brassica juncea) were investigated. Triton X-100 and Tween 80 were individually applied to test pots in which the soil had been earlier spiked with 500 mg kg(-1) of used engine oil, 500 mg kg(-1) of PbCl(2) and 50 mg kg(-1) of CdCl(2). For he application of Tween 80 to the soil, the fractions of rhizodegraded oil and the fractions of removed metals from the soil were well correlated. On the other hand, such a correlation did not exist between the fractions of rhizodegraded oil and the fractions of removed metals for the application of Triton X-100 to the soil. It was observed that Triton X-100 caused a significant decrease in basal soil respiration (BSR) which can be attributed to a reduction in microbial activity. This, in turn, resulted in a reduction of the rhizodegraded oil fraction. Tween 80 proved to be effective in the rhizodegradation of oil under aerobic conditions. Further, this surfactant seems to have the positive effect on the soil microbial population when viewed in terms of BSR.

The biodegradation of cable oil components: impact of oil concentration, nutrient addition and bioaugmentation

The effect of cable oil concentration, nutrient amendment and bioaugmentation on cable oil component biodegradation in a pristine agricultural soil was investigated. Biodegradation potential was evaluated over 21 d by measuring cumulative CO(2) respiration on a Micro-Oxymax respirometer and (14)C-phenyldodecane mineralisation using a (14)C-respirometric assay. Cable oil concentration had a significant effect upon oil biodegradation. Microbial respiratory activity increased with increasing cable oil concentration, whereas (14)C-phenydodecane mineralisation decreased. Bioaugmentation achieved the best cable oil biodegradation performance, resulting in increases in cumulative CO(2) respiration, and maximum rates and extents of (14)C-phenyldodecane mineralisation. Generally, nutrient amendment also enhanced cable oil biodegradation, but not to the extent that degrader amendment did. Cable oil biodegradation was a function of (i) cable oil concentration and (ii) catabolic ability of microbial populations. Bioaugmentation may enhance cable oil biodegradation, and is dependent upon composition, cell number and application of catabolic inocula to soil.

Harmonisation of chemical and biological process in development of a hybrid technology for treatment of recalcitrant metalworking fluid

Disposal of operationally exhausted metalworking fluids (MWFs) is enormously challenging. In this study the feasibility of employing a sequential Fenton-biological oxidation for the treatment of recalcitrant components of MWF wastewater was investigated. A statistical experimental design was employed to address Fenton reagent (H₂O₂, Fe²⁺) dose optimisation which ensured minimal concentrations of the reagents, thus making the treatment environmentally less toxic to subsequent biological steps and economically viable. This was achieved by employing a five-level-two-variable central composite experimental design. The results demonstrated that Fenton pre-treatment of the MWF effluent greatly improved biodegradability index (BOD₅)/COD increased from 0.160 to 0.538) with a synchronous lowering in the toxicity of the wastewater, making the recalcitrant component more amenable to subsequent biological treatment. An overall decrease of 92% and 86% in chemical oxygen demand (COD) and total organic carbon (TOC), respectively, was achieved by the two-step treatment method developed.

Toxicity and biodegradation in sandy soil contaminated by lubricant oils

The objective of this study was to evaluate the environmental behavior of different types of automotive lubricant oils. Based on respirometry assays the biodegradability was monitored, and toxicological tests were executed to assess the lubricants toxicity before and after microbial activity. Used oil was the most biodegradable, however, it was the most toxic. Also, all lubricants presented toxicity even after biodegradation due to 40% Eruca sativa germination inhibition and a low LC50 to Eisenia foetida (0.50-0.25 mL). Moreover, used automotive lubricants have a high toxicity because of polycyclic aromatic hydrocarbons concentration that establishes them as a potential carcinogen.