Background: Unlike petroleum-based synthetic plastics, biodegradable biopolymer generation from industrial residue is a key strategy to reduce costs in the production process, as well as in the waste management, since efficient industrial wastewater treatment could be costly. In this context, the present work describes the prospection and use of bacterial strains capable to bioconvert cassava starch by-product into biodegradable polyhydroxyalkanoates (PHAs). Results: The first step of this study was the bacterial competence screening which was conducted with 72 strains covering 21 Bacillus and related species. The microorganism growth in a medium with a starch substrate was measured by an innovative MTT assay, while the ability of the bacteria to secrete amylase and produce PHA was evaluated by the Nile Red Dye method. Based on growth and potential for PHA production, four isolates were selected and identified as Bacillus megaterium by 16S rRNA sequencing. When cultivated in hydrolyzed cassava starch by-product, maximum production reached 4.97 g dry biomass/L with 29.7% of Poly-(3-hydroxybutyrate) (characterized by FTIR). Conclusions: MTT assay proved to be a reliable methodology for monitoring bacterial growth in insoluble media. Selected amylolytic strains could be used as an alternative industrial process for biodegradable plastics production from starchy residues, reducing costs for biodegradable biopolymer production and wastewater treatment operations.

Os dados utilizados neste estudo são originários de um monitoramento ambiental realizado na enseada do Saco dos Limões, Florianópolis, Santa Catarina, Brasil. Neste monitoramento foram coletadas amostras da ictiofauna, sendo separados para análise um total de 3820 exemplares de Cetengraulis edentulus Cuvier, 1828, capturados em 17 coletas, no período compreendido entre julho de 1999 e abril de 2001. A análise dos dados permitiu estimar parâmetros populacionais e reprodutivos importantes como o comprimento de primeira maturação (118 mm para sexos grupados, 112 e 118 mm para machos e fêmeas, respectivamente), as distribuições de freqüências de comprimento, a relação peso-comprimento (Pt = 0,0000003 x Ct 3,67º8), a proporção sexual ao longo do tempo, a variação sazonal dos estádios de maturação gonadal, o índice gonadossomático, o fator de condição e o fator de condição somático, o ciclo reprodutivo e o período de desova, sendo também determinada a participação da espécie no ictioplâncton. Foram determinadas as correlações entre os parâmetros biológicos e os ambientais de temperatura e salinidade da água, superficial e de fundo. Constatou-se que a espécie utiliza o ambiente de estudo ao longo de todo seu ciclo de vida, tanto para reprodução quanto para a alimentação e o crescimento, e está estrategicamente adaptada às condições ambientais e biológicas da área de estudo.

Data used in this study are from a monitoring program conducted in the Saco dos Limões cove, Florianópolis, Santa Catarina, Brazil. In this program, fish fauna were collected in 17 surveys from July 1999 to April 2001. For this study, 3820 individuals of Centengraulis edentulus Cuvier, 1828 were examined regarding population and reproductive parameters, such as, length at sexual maturity (118 mm for the combined sexes, 112 mm for males and 118 mm for females), frequency distributions for total length, length-weight relationship (Wt = 0,0000003 x Lt 3,67º8), sex ratio, seasonal variation of the gonad maturation stages, gonadosomatic index, condition factor, somatic condition factor, reproductive cycle and timing of spawning. Ichthyoplankton samples were also examined in order to verify the sharing of this species in such samples. It was determined correlations between biological and environmental parameters, such as, surface and bottom temperature, and salinity in the water column. The results revealed that Centengraulis edentulus is strategically fitted to the environmental and biological conditions found in this area, which is used during its life cycle for reproduction, feeding and growing.