Abstract
SummaryHeavy vacuum gas oil (HVGO) is a complex and viscous hydrocarbon stream that is produced as the bottom side product from the vacuum distillation units in petroleum refineries. HVGO is conventionally treated with thermochemical process, which is costly and environmentally polluting. Here, we investigate two petroleum biotechnology applications, namely valorization and bioupgrading, as green approaches for valorization and upgrading of HVGO. The Pseudomonas aeruginosa AK6U strain grew on 20% v/v of HVGO as a sole carbon and sulfur source. It produced rhamnolipid biosurfactants in a growth‐associated mode with a maximum crude biosurfactants yield of 10.1 g l−1, which reduced the surface tension of the cell‐free culture supernatant to 30.6 mN m−1 within 1 week of incubation. The rarely occurring dirhamnolipid Rha–Rha–C12–C12 dominated the congeners’ profile of the biosurfactants produced from HVGO. Heavy vacuum gas oil was recovered from the cultures and abiotic controls and the maltene fraction was extracted for further analysis. Fractional distillation (SimDist) of the biotreated maltene fraction showed a relative decrease in the high‐boiling heavy fuel fraction (BP 426–565 °C) concomitant with increase in the lighter distillate diesel fraction (BP 315–426 °C). Analysis of the maltene fraction revealed compositional changes. The number‐average (Mn) and weight‐average (Mw) molecular weights, as well as the absolute number of hydrocarbons and sulfur heterocycles were higher in the biotreated maltene fraction of HVGO. These findings suggest that HVGO can be potentially exploited as a carbon‐rich substrate for production of the high‐value biosurfactants by P. aeruginosa AK6U and to concomitantly improve/upgrade its chemical composition.
Highlights
Biosurfactants are surface-active microbial products that are getting increasing interest due to their superior physicochemical properties, environmental compatibility as compared with synthetic surfactants (Soberon-Chavez and Maier, 2011), and the wide range of industrial and environmental applications
The number-average (Mn) and weight-average (Mw) molecular weights, as well as the absolute number of hydrocarbons and sulfur heterocycles were higher in the biotreated maltene fraction of Heavy vacuum gas oil (HVGO). These findings suggest that HVGO can be potentially exploited as a carbon-rich substrate for production of the high-value biosurfactants by P. aeruginosa AK6U and to concomitantly improve/ upgrade its chemical composition
To investigate the ability of the P. aeruginosa AK6U strain to grow on HVGO and produce biosurfactants, we cultured the strain in sulfur-free mineral salts medium a 2017 The Authors
Summary
Biosurfactants are surface-active microbial products that are getting increasing interest due to their superior physicochemical properties, environmental compatibility as compared with synthetic (petroleum-based) surfactants (Soberon-Chavez and Maier, 2011), and the wide range of industrial and environmental applications. The biosurfactants market share is projected to reach more than two billion US $ by 2020 with the production of ca 462 kilo tons (De Almeida et al, 2016). Biosurfactants have not been able to compete economically with their synthetic counterparts due to high production costs. To overcome this problem, at least in part, low-value and inexpensive carbon-rich feed stocks, such as agricultural and industrial wastes/residues, have been used by many investigators as carbon sources for biosurfactants production (Banat et al, 2014). Ca 725 million metric tons of residue, resulting from the vacuum distillation units, is processed through various conversion processes (Sahu et al, 2015). Petrochemical wastes and processing residues are potential substrates for biosurfactants production, they have not received the proper attention
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