Optimizing the growth of Haematococcus pluvialis based on a novel microbubble-driven photobioreactor

Haematococcus pluvialis, the richest bioresource for natural astaxanthin, encounters a challenge of achieving high growth rate when it comes to mass biomass production. Based on the substrate consumption model and Redfield ratio, rapid algae growth benefits from a proper carbon supply. However, the conventional cultivation schemes with limited carbon dioxide (CO₂) supply and inefficient carbon mass transfer could have constrained the carbon capture and growing ability of H. pluvialis. We hypothesize that optimal H. pluvialis growth improvement may be achieved by efficient CO₂ supply. Here, in this study, we first identified the carbon consumption of H. pluvialis during exponential growth. Then, a novel microbubble-driven photobioreactor (MDPBR) was designed to satisfy the carbon demand. The novel microbubble photobioreactor improves the CO₂ supply by reducing bubble size, significantly elevating the CO₂ mass transfer. With only 0.05 L min^-1 of gas flow rate, higher cell growth rate (0.49 d^-1) has been achieved in MDPBR.