Desulphurisation of sour crude oil by sulphur utilising bacteria through 4S pathway

Abstract

Crude oil is the most highly demanded raw fuel source in a global value chain. Biodesulphurisation (BDS) has a good potential alternative over hydrodesulphurisation (HDS), particularly for upgrading and improving sour crude oil with low capital needs. HDS displayed removal of non-aromatic heterocyclic sulphur that change the calorific value of the oil while BDS performed specific removal of only polyaromatic sulphur heterocyclic that conserved the fuel value ofthe crude oil. Eight potential desulphurising bacteria through the targeting of C-S bond specific cleavage in sulphur removal from dibenzothiophene (DBT) and Iraqi sour crude oil have been successfully characterised using I6S rDNA sequences analyses. S.maltophilia CNKI showed the greatest desulphurisation and formation rate of 2-HBP rate in comparison with other bacteria tested. Maximum BDS rate (12/umol/gDCW h-l) was obtained using DBT in the culture at pH 7.0, added with 5 g/L glucose as carbon source, 0.2% (w/v) casein and/or malt extract as nitrogen source and incubated with agitation (180 rpm) at 30oC. S. maltophilia CNKI also displayed the greatest sour crude oil desulphurisation activity. Removal of organic sulphur from crude oil was improved by ~50% in the bioreactor compared to those in the shake flasks. Desulphurisation activity by CNKI was further enhancedusing the stirred tank and airlift reactor with 10% (v/v) loading of AHD and BSH crude oil, with the total sulphur reduction rate of 47.21% and 52.61%, and the reduction of organic sulphur of about 50.20 and 71.84% based on GC/FID analyses.