The environment is a very important component necessary for the existence of both man and other biotic organisms. The degree of sustainability of the physical environment is an index of the survival and well-being of the entire components in it. Additionally, it is not sufficient to try disposing toxic/deleterious substances with any known method. The best method of sustaining the environment is such that returns back all the components (wastes) in a recyclable way so that the waste becomes useful and helps the biotic and abiotic relationship to maintain an aesthetic and healthy equilibrium that characterizes an ideal environment. In this study, the method investigated includes biological method of environmental sustainability which seeks to investigate the various biotechnological tools (biotools) in current use and those undergoing investigations for future use.

Pollu t ion Con t r ol & Biot ech n ology Un it , Depa rt m en t of Bioch em ist ry, U n iver sit y of Niger ia , Nsu kk a , E n u gu St a t e, Niger iaReceived 11 Novem ber 1998; a ccep ted 1 J u ly 1999. The a u t h or wish es t o t h a n k Ch ief Tech n ologist E n gr. J. U. Or a egbu n a a n d J. C. N wok edi for in st r u m en t a t ion , Mr s. C. O. Sibeu du of t h e Depa r t m en t of Pet r oleu m Resou r ces, Niger ia n N a t ion a l Pet r oleu m Cor por a t ion , Mosco Roa d, Por t H a r cou r t, for a ssist a n ce in secu r ing t h e Bon n y light cr u de oil a n d r eleva n t liter a t u r e, a n d Ok or on k wo Ka n u (MNI A), t h e pr incipa l a r ch it ect , Design Modu les, E n u gu , Niger ia, for e-m a il fa cility. Th is wor k wa s su p por t ed in pa r t by t h e Un iver sit y of Niger ia Sen a t e Resea r ch Gra n t No 93/101.Addr ess cor r es pon den ce t o I. N. E. On wu r a h , Pollu t ion Con t r ol & Biot ech n ology Un it , Dept . of Bioch em istr y, Un iver sit y of Niger ia , Nsu k ka , E n u gu St a t e, Niger ia.

Nitrogen is one of the most limiting inorganic nutrients in the process of bioremediation of crude oil-polluted environments. Enhanced remediation of crude oil polluted soil was achieved, in situ, by accelerating the biodegradation process through seeding with adapted Azotobacter which not only acted as supplier of ®xed nitrogen to the indigenous crude oil-degrading bacteria, but also performed some co-metabolic activities. This work describes the capability of Azotobacter in providing activities that are useful in the bioremediation of crude oil-polluted soil and biological nitrogen ®xation when in association with indigenous oil-degrading bacteria.

The short term toxicity in Clarias albopunctatus (Lamonte and Nicole, 1927) exposed to sub-lethal concentrations of Roundup was studied. A total of 36 fish were divided into 3 groups in a static bioassay model. Fish in 2 test groups were exposed to 5 and 15 ppm, respectively, of Roundup while fish in the control group were not exposed to the toxicant. Six fish per group were bled exhaustively (each) at 48 h and at 96 h while the livers and gills were harvested at 96 h for histological studies. The results showed that serum concentrations of total and conjugated bilirubin increased significantly (p<0.05) in a dose-and time-dependent manner. Serum concentrations of alanine and aspartate aminotransferases and alkaline phosphatase were also significantly (p<0.05) elevated in the test fish. Similarly, serum concentrations of creatinine and urea were significantly (p<0.05) elevated in a dose-dependent manner. Histomorphologic studies of the liver and gills showed marked destruction of their architecture in the test fish, thus corroborating the data from the biochemical analyses. Short term exposure of Clarias albupunctatus to sub-lethal concentrations of Roundup was found to be toxic to the fish.

A mixed culture of compatible hydrocarbonoclastic and diazotrophic bacteria, each at a density of 10 8 organisms cm −3 , was developed for optimised bioremediation of crude oil-contaminated soil. The hydrocarbonoclastic bacterium, Pseudomonas sp and the diazotroph, Azotobacter vinelandii, were both isolated from a previously crude oil-contaminated soil and thereafter modelled as a unit of mutualistic consortium in situ. Stabilisation of the consortium and hence the optimised bioremediation process occurred when the bacterial growth attained a pseudo-steady state condition. This was considered to be as a result of a symbiotic association between A vinelandii and the Pseudomonas sp in which A vinelandii produced the required concentration of fixed nitrogen compounds required for the growth of the Pseudomonas sp. Enhancement in biodegradation, due to stimulated growth of Pseudomonas sp and co-metabolic activity of A vinelandii, was mathematically evaluated as the difference in the specific growth rates (µ) between the consortium Pseudomonas sp/A vinelandii and Pseudomonas sp alone. The proportion of petroleum hydrocarbons degraded by the consortium from the contaminated soil ranged between 66.83 and 69.6% as compared with that of a pure culture of Pseudomonas sp (23.2-44.45%). Hence, beyond their role in biological nitrogen fixation, diazotrophs may be used to contribute to bioremediation of crude oil-contaminated land.