PHB in cyanobacteria: analyzing production through images processing and FT-IR techniques

Cyanobacteria have gained significant attention in recent years due to their ability to produce a variety of valuable compounds. One such compound is polyhydroxybutyrate (PHB), a biodegradable polymer with immense potential in various industrial applications. Given that PHB is stored intracellularly, a dedicated process is needed to extract and measure the biopolymer content. Nevertheless, this process is time consuming and requires environmental hazardous chemicals, such as chloroform. In the present work, we present two complementary methods developed to analyze and quantify PHB production in cyanobacteria microbiomes. The first one consists in an image processing applied on images obtained from Transmission Electronic Microscope (TEM), that can potentially be applied to others type of microscope images as confocal, for qualitative assessment. In this case, a segmentation process allows differentiating PHB grains inside cyanobacteria cells. A metric is then established by computing pixels area taken up by PHB in the whole image and in cyanobacteria cells. A good correlation (higher than 0.65) is observed for all indicators as regard to PHB content. The second method relies on Fourier-transform infrared (FTIR) spectroscopy, as a non-destructive and rapid method to analyze PHB. Absorption peaks due to carbonyl, and Amide I and II group characteristics of monomer structure in PHB and cyanobacteria´s protein are observed. A correlation coefficient r² of 0.96 is reached with the linear regression. A comparison between the two techniques is presented and their main advantages for PHB production optimization are explained. ------------------------------------------------------------------------------------------------------------------------.