The bacterial consortium MPD-M, isolated from sediment associated with Colombian mangrove roots, was effective in the treatment of hydrocarbons in water with salinities varying from 0 to 180 g L(-1). Where the salinity of the culture medium surpassed 20 g L(-1), its effectiveness increased when the cells were immobilized on polypropylene fibers. Over the range of salinity evaluated, the immobilized cells significantly enhanced the biodegradation rate of crude oil compared with free-living cells, especially with increasing salinity in the culture medium. Contrary to that observed in free cell systems, the bacterial consortium MPD-M was highly stable in immobilized systems and it was not greatly affected by increments in salinity. Biodegradation was evident even at the highest salinity evaluated (180 g L(-1)), where biodegradation was between 4 and 7 times higher with immobilized cells compared to free cells. The biodegradation of pristane (PR) and phytane (PH) and of the aromatic fraction was also increased using cells immobilized on polypropylene fibers.

Two novel and versatile bacterial consortia were developed for the biodegradation of hydrocarbons. They were isolated from crude oil from the Cormorant Field in the North Sea (MPD-7) and from sediment associated with mangrove roots (MPD-M). The bacterial consortia were able to degrade both aliphatic and aromatic hydrocarbons in crude oils very effectively in seawater (35 g/L NaCl) and synthetic media containing 0 to 100 g/L NaCl (1.7 M). Salinities over twice that of normal seawater decreased the biodegradation rates. However, even at the highest salinity biodegradation was significant. Ratios of nC17 to pristane and nC18 to phytane were significantly lowered across the range of salinity. The lowest values were at 0 and 20 g/L (0.34 M). Phytane was degraded in preference to pristane. The degradation of these compounds was constant over the salinity range, with evidence of a slight increase for consortium MPD-M with increasing salinity. In general, the consortium isolated from mangrove root sediments was more efficient in metabolizing North Sea crude oil than the consortium isolated from Cormorant crude oil. The 5 strains that comprise MPD-M have been tentatively identified as species of the genera Marinobacter, Bacillus, and Erwinia. This is the first report of hydrocarbon-degrading consortia isolated from crude oil and mangrove sediments that are capable of treating oily wastes over such a wide range of salinity.

Presence of thiocyanate (SCN -) is a problem of considerable interest in many industrial wastewaters, where this contaminant often appears accompanied by secondary sources of carbon, nitrogen and/or sulphur. In order to understand the effect of these compounds on the biodegradability of SCN -, this work investigates how the bacterium Pararacoccus thiocyanatus utilises the three elements that form the molecule of thiocyanate and compare this behaviour with those obtained in presence of other sources of N, S and C. Result showed that the bacterium was capable of utilizing thiocyanate as the sole substrate, achieving specific biodegradation rates of approximate 1.20 mg SCN -(mg cell·h) -1 and eliminating initial thiocyanate concentrations up to 5,000 mg L -1 . Experimental data were successfully fitted to a Teisser model, assuming the existence of substrate inhibition obtaining values of μ max of 0.059 h -1 , K s of 790 mg L -1 and K i of 6,520 mg L -1 for free mineral medium. Presence of additional carbon and nitrogen sources implied catabolic repression of the biodegradation of thiocyanate. In this case, only concentrations lower than 3,500 mg L -1 could be treated, obtaining specific degradation rates of around 0.70 mg SCN -·(h·mg cell) -1 . Tessier model values showed a higher maximum specific growth rate (0.344 h -1 ), changing also the values for affinity and inhibition constants (1,150 mg L -1 and 1,730 mg L -1 , respectively).