EVALUATION OF SOIL GRAM-NEGATIVE BACTERIA YIELDING POLYHYDROXYALKANOIC ACIDS FROM CARBOHYDRATES AND PROPIONIC-ACID

A screening programme was developed leading to the isolation of 75 str ains of soil gram-negative bacteria which are able to produce polyhydr oxyalkanoic acids (PHA) from sugar-cane derivatives. The evaluation of these strains was performed with regard to their efficiency in conver ting carbohydrates or propionic acid into PHA constituents. Several st rains 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 th e theoretical value when converting carbohydrates into PHB and accumul ated at least 50% of the cell dry weight as PHB. Ten strains incorpora ted 3-hydroxyvaleric acid units into the polymer from propionic acid o f which 3 gave yields comparable to those of Alcaligenes eutrophus.