In this investigation, a sugarcane agroecosystem at a coastal tableland, in the northeast
of Brazil, was screened to obtain bacteria strains able to synthesize
poly-b-hydroxyalkanoates (PHA), using sucrose as the main carbon source. The potential
to synthesize PHA was tested qualitatively by Sudan Black staining of colonies growing
in different carbon sources: sucrose, glucose, fructose, propionate and cellulose. In a
typical sugarcane crop management system, the plantation is burned before harvesting
and vinasse, a by-product of alcohol production, is used in a fertirrigation system causing,
probably, selective pressures on the microbiota of natural environments. Eighty-two
bacteria strains, belonging to 16 different genera and 35 different species, were isolated.
The data showed that 11 strains (ca 13%), nine of which belonging to the genus
Pseudomonas, presented a strong Sudan Black staining in several carbon sources tested
and, simultaneously, showed multiple resistance to antibiotics. Resistance to antibiotics
is an advantageous feature for the biotechnological production of PHAs. The total number
of isolates with multiple resistance to antibiotics was 73, and 38% of them belong to the
genus Pseudomonas. Among the isolates, ca 86% and 43% grew in the presence of
10-100 U/ml of penicillin and/or 100-300 mg/ml of virginiamycin, respectively. These
antibiotics are utilized in the alcohol distillery we investigated. The results suggest that
some agroecosystem environments could be considered as habitats where bacteria are
submitted to nutritional unbalanced conditions, resulting in strains with potential ability
to produce PHAs, and also, to an increase in the microbial diversity.