Biochemical Composition of Chlorella Sorokiniana Grown in a Novel Design of Hybrid Photobioreactor

Abstract

The aim of this study was to assess the feasibility of a 180 L photobioreactor in which a submerged ultrafiltration system was used to maintain continuous nutrient inflow without biomass loss from the culture. After exponential growth, approximately 15% of the total volume was removed and replaced with a modified medium to induce algal physiological responses as a biochemical manipulation procedure. In this system, Chlorella sorokiniana was kept under healthy conditions, according to protein: carbohydrate ratio. C. sorokiniana was grown exponentially for 4 days up to 8.9x10 6 cells mL-1. The culture medium used for biochemical manipulation (72 h exposure) consisted of LC Oligo medium without nitrates or phosphates, and with 7x10-7 molL-1 total copper. The results confirmed the effectiveness of the submerged membrane and showed that algae exposure to a stressing medium resulted in intracellular carbohydrate increase, thus protein: carbohydrate (P:C) ratios, and affected lipid class composition. This novel photobioreactor configuration has the potential to improve microalgal yields and/or specific intracellular constituents, inasmuch as biochemical manipulation of the biomass is facilitated and the continuous system is operated without biomass loss.