Mônica A. Rodrigues

Evaluation of soil gram-negative bacteria yielding polyhydroxyalkanoic acids from carbohydrates and propionic acid

Abstract A screening programme was developed leading to the isolation of 75 strains of soil gram-negative bacteria which are able to produce polyhydroxyalkanoic acids (PHA) from sugar-cane derivatives. The evaluation of these strains was performed with regard to their efficiency in converting carbohydrates or propionic acid into PHA constituents. Several strains were able to use sucrose as well as glucose and fructose to grow and afterwards to accumulate poly-(3-hydroxybutyric acid) (PHB) with promising yields. Seven strains were found to have more than 80% of the theoretical value when converting carbohydrates into PHB and accumulated at least 50% of the cell dry weight as PHB. Ten strains incorporated 3-hydroxyvaleric acid units into the polymer from propionic acid of which 3 gave yields comparable to those of Alcaligenes eutrophus.

Biosynthesis of poly (3-hydroxybutyric acidco-3-hydroxy-4-pentenoic acid) from unrelated substrates byBurkholderia sp.

From soil, two strains ofBurkholderia sp. were isolated that synthesized and accumulated a copolyester of 3-hydroxybutyric acid and 3-hydroxy-4-pentenoic acid from single, unrelated carbon sources such as surcose or gluconate. Strain IPT77B, for instance, accumulated from gluconate poly(3-hydroxybutyric acidco-3-hydroxy-4-pentenoic acid) up to 70% (w/w) of the cellular dry matter, and 3-hydroxy-4-pentenoic acid contributed up to 6.9 mol 100/mol constituents. The occurence of the constituent with the vinyl pendant group in the polyester was confirmed by gaschromatographic and nuclear magnetic resonance analysis.

Prata: Breve histórico, propriedades e aplicações

Silver: Brief history, properties and applications Silver, a malleable metal, ductile, bright, known since prehistoric times is widely used in photographic industry, of jewelry and decorative objects. Due to its remarkable physical and chemical properties, new applications have emerged. Considering the importance of this element, this article describes their history, properties and applications.