Valorization of lubricant-based wastewater for bacterial neutral lipids production: Growth-linked biosynthesis

Abstract

Lipids produced by microorganisms are currently of great interest as raw material for either biofuels or oleochemicals production. Significant biosynthesis of neutral lipids, such as triacylglycerol (TAG) and wax esters (WE) are thought to be limited to a few strains. Hydrocarbonoclastic bacteria (HCB), key players in bioremediation of hydrocarbon contaminated ecosystems, are among this group of strains. Hydrocarbon rich wastewaters have been overlooked concerning their potential as raw material for microbial lipids production. In this study, lubricant-based wastewater was fed, as sole carbon source, to two HCB representative wild strains: Alcanivorax borkumensis SK2, and Rhodococcus opacus PD630. Neutral lipid production was observed with both strains cultivated under uncontrolled conditions of pH and dissolved oxygen. A. borkumensis SK2 was further investigated in a pH- and OD-controlled fermenter. Different phases were assessed separately in terms of lipids production and alkanes removal. The maximum TAG production rate occurred during stationary phase (4 mg-TAG/L h). The maximum production rate of WE-like compounds was 15 mg/L h, and was observed during exponential growth phase. Hydrocarbons removal was 97% of the gas chromatography (GC) resolved straight-chain alkanes. The maximum removal rate was observed during exponential growth phase (6 mg-alkanes/L h). This investigation proposes a novel approach for the management of lubricant waste oil, aiming at its conversion into valuable lipids. The feasibility of the concept is demonstrated under low salt (0.3%) and saline (3.3%) conditions, and presents clues for its technological development, since growth associated oil production opens the possibility for establishing continuous fermentation processes.

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

“…Production of bacterial storage lipids during biological treatment of hydrocarbon-based wastewaters has been recently proposed as a way to make management of these wastes more economic and environmentally sustainable (Da Silva et al, 2016). Hydrocarbonoclastic bacteria have the ability to degrade a wide range of hydrocarbon compounds: branched, unbranched and cyclic alkanes as well as aromatics, namely monocyclic aromatic hydrocarbons (MAH) and polycyclic aromatic hydrocarbons (PAH).…”

“…Alcanivorax borkumensis SK2 accumulated predominantly TAG when cultivated on pyruvate and similar levels of TAG and WE with hexadecane (Manilla-P erez et al, 2011). More recently, A. borkumensis SK2 fed with lubricant-based wastewater, produced the highest TAG levels in stationary growth phase, whereas maximum production of WE-like compounds was achieved during exponential growth phase (Da Silva et al, 2016).…”

Sequencing batch airlift reactors (SBAR): a suitable technology for treatment and valorization of mineral oil wastewaters towards lipids production

“…It is a more cost-effective method, allowing to remove the small suspended oil particles that cannot be eliminated otherwise and environmental friendly, since it relies in bacteria capability to transform hydrocarbons into nontoxic by-products such as carbon dioxide (CO 2 ), water or bacterial reserve compounds (Dong et al, 2011;Fakhru'l-Razi et al, 2009). Several works have been focused on the aerobic treatment of hydrocarbon contaminated wastewaters since it occurs at a faster rate and is more efficient than under anaerobic conditions (Da Silva et al, 2016;Heider et al, 1998;Sudmalis et al, 2018). Mineral oil wastewaters, like for instance PW and LW, differ from each other relatively to the type and content of hydrocarbons, salinity levels and presence of some other specific compounds.…”

“…Mineral oil wastewaters, like for instance PW and LW, differ from each other relatively to the type and content of hydrocarbons, salinity levels and presence of some other specific compounds. For example, PW consists mainly on aliphatic hydrocarbons from C11 to C40, which are more easily biodegradable than aromatic hydrocarbons (Sudmalis et al, 2018), while LW is composed by a complex matrix that includes a mixture of straight-chain alkanes ranging from C10 to C34 and a complex and unresolved hydrocarbon mixture (Da Silva et al, 2016). Another important feature of mineral oil wastewaters is the salinity levels which in the case of offshore PW can be challenging when a biological treatment is applied.…”

Production of added value bacterial lipids through valorisation of hydrocarbon-contaminated cork waste

“…Because this genus possess many catabolic genes conferring the capacity to transform a wide variety of pollutants including hydrocarbons, (Larkin et al, 2010), several Rhodococcus strains are being study for bioremediation of hydrocarbon-contaminated sites and industrial wastewaters (Auffret et al, 2014). Rhodococcus species are also interesting because they can produce storage lipids compounds, especially TAG, during cultivation on several carbon sources, including single hydrocarbons (Alvarez, 2003) and waste hydrocarbon mixtures (Da Silva et al, 2016). Bacterial lipids are valuable compounds with potential to replace fossil resources in many industrial processes, in particularly in biofuels production.…”