PRODUCCIÓN DE IMIDASAS POR LAS BACTERIAS DEL TRACTO DIGESTIVO DE Eisenia foetida

Abstract

The imidase production in bacteria has been reported, some may be involved in the degradation of polymers or toxic compounds like the acrylamide. Polyacrylamides are polymers formed mainly by units of acrylamide. To date there is not sufficient information showing that the polyacrylamide is toxic; however acrylamide is highly toxic, at high concentrations, affects the central nervous system. Polyacrylamides are used in industrial processes such as flocculation and in agriculture to improve grounds. One of bioremediation processes for efficient degradation of industry biosolids is the vermicompost. Earthworms have been used in many bioremediation processes due to their ability to accumulate and/or degrade toxic pollutants, ease of handling in the laboratory and the ability to transform waste materials into worm castings which is useful like compost in agricultural and urban zones. Eisenia foetida has been reported as the best earthworm to transform organic waste or toxic residues, in addition has a great tolerance to the temperature. Also it owns an abundant bacterial flora in its gut, which helps its digestive metabolism as well as to degrade toxic compounds. Some of these bacteria can produce imidase enzymes, that degrade acrylamide or polyacrylamide. As such, it is important to isolate and identify strain (s) producer (s) of imidases. In this thesis 42 bacterial strains of the digestive tract of E foetida were isolated. And identified 13 bacterial strains to genus and species nivel by means of the molecular characterization of the 16S rRNA: Kocuria rosea, Serratia marcescens, Planomicrobium sp., Arthrobacter oxydans, Microbacterium schleiferi, Bacillus subtilis, Arthrobacter luteolus, Crocinobacterium jejui, Paenibacillus spp., Micrococcus yunnanensis, Bacillus weihensthephanensis, Janibacter melonis and Kocuria sp. All grew on a minimum medium with 1 g / L of acrylamide as the sole carbon source. Seven of these strains grew in minimum culture media with 3 g/L of acrylamide and 1 g/L polyacrylamide (B. subtilis, A. luteolus, C. Jejui, S. marcescens, K. rosea, B. weihensthephanensis and Planomicrobium sp.). The A. luteolus strain displayed the highest value growth rate of acrylamide with a value of 0.046 h-1and with polyacrylamide was S. marcescens strain with a value of 0.029 h-1. The best yield Yps was obtained with the B. weihensthephanensis, using acrylamide and polyacrilamide.The ammonia production which is the product of the degradation of acrylamide and polyacrylamide is not associated with the growth of bacterial strains used in this studyB. subtilis and B. weihensthephanensis displayed the greater cell growth and the highest percentage of acrylamide removal (97%), according to the production of ammonia and the highest value of imidase activity of the seven bacterial strains studied. B. subtilis and Planomicrobium sp., were those that grew better in the cultures with polyacrylamide (1 g/L) and these strains presented the major production of ammonia and higher value of enzyme activity. Likewise, it demonstrated that the production of imidasa (s) in the seven bacterial strains grown with acrylamide or polyacrylamide, by means determining its enzymatic activity, the removal of these compounds and ammonia production.