Screening of polyhydroxyalkanoates (PHA)-producing bacteria from soil bacteria strains

Abstract

Plastic wastes and petrochemical-based polymer materials have become a serious problem to the environment due to the characteristics of these materials that are difficult to degrade in nature. Polyhydroxyalkanoates (PHA) is one type of biodegradable plastics that have a great potential to replace the widely-used hydrocarbon plastics since it will decompose completely into carbon dioxide and water after burial for several months in the soil. PHA can be produced by microorganisms such as bacteria and algae through a fermentation process. The objective of this research is to obtain bacteria that can produce PHA. Screening was carried out by two sequential steps, qualitative and followed by quantitative methods. An amount of 29 bacteria strains isolated from Indonesians soil were screened for this purpose. The qualitative screening was conducted by growing the bacteria in a specific medium containing Nile red dye. The results showed that 19 strains were positive, generated pink to orange colonies under UV light at 235 nm. It was also confirmed by fluorescence microscope. The quantitative screening was performed by measuring the intracellular materials (predicted as PHA) of the bacterial cells by gravimetric method. The results indicated that the highest average of PHA content was 52.9%, 35.6% and 35.4 of dried cell weight, respectively for the Burkholderia sp B73, Bacillus sp B58, Bacillus toyonensis B50 and Staphylococcus cohni B66.