Production of polyhydroxybutyrate (PHB) in Scenedesmus acutus using a low-cost substrate

The importance of conventional plastics is undeniable; however, their non-biodegradability makes them one of the biggest environmental problems. Among the alternatives to mitigate environmental damages, the production of polyhydroxyalkanoates (PHB) provides a biodegradable solution, additional to their mechanical and thermal properties, making them accessible to a wide variety of applications. In general, biopolymers accumulate as energy and carbon storage material in microorganisms such as bacteria and microalgae. In the present study, the impact of different sources like carbon, glucose, nitrogen and sodium was tested on the production of PHB in the cultures of the microalgae S. acutus . To evaluate the effect of the variables, a fractional Taguchi experimental design was devised and executed, thus, 16 experimental runs and 3 replicas in each treatment were considered. Results showed calculated concentrations of the biopolymer in a range from 7.5–34.7% w/w dry weight. Additionally, the PHB was identified by spectroscopic and thermogravimetric analysis. Statistical analysis was performed using Minitab 16, where differences in biomass production, PHB concentration in g/L and the percentage of PHB were analyzed. Likewise, a Pareto diagram was used to consider the biomass production results, with glucose, biomass-glucose, and biomass-sodium as determining factors in the PHB production. The present research provides significant data on critical factors related with PHA production, for the first time to our knowledge, thus showing Scenedesmus acutus as a PHB producer through low-cost medium providing a promising candidate for industrial scale-up.