Tahereh Nobakht, - Department of Biology, Faculty of Sciences, University of Guilan
Azita Dorri - Department of Biology, Faculty of Sciences, University of Guilan
Akbar Norastehnia - Department of Biology, Faculty of Sciences, University of Guilan

Polyhydroxyalkanoates are biopolymers that are usually accumulated in the form of granular inside the cells of some microorganisms under uneven growth conditions. Polyhydroxybutyrate (PHB) is a polymer of polyhydroxyalkanoates, which has properties similar to synthetic plastics, with the advantage of being biodegradable. In order to compare the production rate of PHB in laboratory conditions of autotrophy, heterotrophy and mixotrophy in microalga Spirulina sp., experiments were conducted with three replications. The microalga was grown within Zarrouk‟s medium. The basic conditions of the culture chamber were regulated at 25 ± 2 °C and 2500 lux light intensity with a 12-hour light period and 12 hours of darkness, under air conditioning treatment. The heterotrophic conditions were determined by wrapping black plastic around the container of samples and mixotrophic conditions by adding 0.1% sucrose as a carbon source in the culture medium. All three culture media were incubated under basic conditions for 20 days and the microalgae were harvested using a centrifuge. Extraction of PHB from microalgae by ultrasonic, centrifuge and chloroform, methanol and hexane solutions was performed in several steps. The presence of PHB was confirmed using Black Sudan coloration and FTIR. The amount of PHB accumulation extracted from microalgae under autotrophic, mixotrophic and heterotrophic conditions were 0.11, 0.16, and 0.26 percent w/w respectively, considering chromatograms resulted from gas chromatography (GC). According to the results, PHB accumulation in heterotrophic conditions appears to be higher than the other two cultures quantitatively.

Biodegradable, Autotrophy, Heterotrophy, Mixotrophy, PHB, Spirulina sp