Poli(3-hidroxibutirato) com propriedades térmicas diferenciadas produzido por Pseudomonas sp. CMM43 degradadora de agrotóxico

Abstract

Bioplastics have been gaining espace in research projects and many are already being produced on an industrial scale and can replace petrochemical polymers of origin, resulting in greater environmental benefit. They also have great biotechnological potential and can be used as raw material for different products depending primarily on the physical, chemical and thermal properties that show. Polyhydroxyalkanoates (PHAs), typical bioplastics completely biodegradable, are polyesters accumulated mainly by a variety of bacteria, as a source of carbon and energy reserve for the cell. The poly(3-hydroxybutyrate) [P(3HB)], is the most studied and most commonly stored as lipophilic PHA granules, reaching levels of 90% of dry cell weight. The aim of this study, was first, to quantify and evaluate the thermal properties of the produced polymer by Pseudomonas sp. CMM43, identified as producing P(3HB), cultivated in simple nutrient medium. Following aimed to optimize the production of P(3HB) by the bacteria in orbital shaker and bioreactor, and to characterize produced biopolymers in different conditions. Initially, was investigated cellular growth phase, changing cultivation parameters in order to increase the concentration of biomass produced and to determine if production is growthassociated. The P(3HB) recovered was identified and characterized. The Pseudomonas sp. CMM43 accumulated, high levels of P(3HB) at 24 h, without any nutrient limitation, suggesting that accumulation of polymer occurs simultaneously on the growth. The maximum content, 70% in the dry cell weight (DCW) was obtained in medium with sucrose, pH 6.5, temperature of 28 º C, 250 rpm and less aeration. The biopolymer presented reduced thermal properties and molecular weight, which allows specific applications in the medical and pharmaceutical area. In a second phase, was tested still in an orbital shaker incubator, media and inoculum concentration for the biopolymer production phase, in the temperature and aeration previously selected. The P(3HB) are recovered were identified and characterized. The maximum polymer yield was 83% in DCW at 48 h, in the medium which 10% (v/v) of inoculum and1% of sucrose was used. Polymers with low molecular weight and with melting temperature less than degradation were obtained, indicating that a characteristic of bacteria, and no influence on the medium or the concentration of inoculum. By the end was evaluated P(3HB) production in bioreactor, using the same medium and culture conditions of the previous study, it was observed a large reduction in the accumulation. In conclusion, Pseudomonas sp. CMM43 has promising conditions for industrial P(3HB) production processes. Despite not having reached high cell concentrations, the strain acumulated high levels (P(3HB)/DCW) for 48 h, without nutrient limitation and using sucrose, quite economical substrate in Brazil. Additionally, synthesizes polymers with different thermal properties that allow specific applicability in the biomedical and pharmaceutical field.