Optimization of the culture medium for massive production of marine microalgae Conticribra weissflogii

Author: Cynthia Maria Oliveira Couto (Currículo Lattes)
Supervisor: Dr Paulo Cesar Oliveira Vergne de Abreu
Co-supervisor: Dr Fabio Roselet

Abstract

Microalgae are a potentially rich source of several components of commercial interest. However, the viability of their production depends on several factors, among them, the costs of the means of cultivation. For this reason, there is a great need to develop less costly, but efficient means. Few studies have tested the replacement of laboratory culture media, with compounds with a high degree of purity, by less pure and more economical elements such as fertilizers. The objective of this study was to develop a low-cost cultivation medium for the mass production of the microalgae Conticribra (Thalassiosira) weissflogii and to evaluate the quantity and composition of the biomass produced. For that, it was first evaluated which nitrogen source (ammonia or urea) is the most appropriate for the growth of the species. Subsequently, through the design of experiments methodology, which elements of the culture medium are essential for the growth of the species were evaluated and then their concentrations were optimized. A second optimization was carried out by adjusting the concentrations of the elements for a better cost/benefit ratio of the new formulated medium. In addition, an experimental validation of the empirical model was performed. Finally, analyzes of proteins, lipids and fatty acid profiles of the biomass were performed in the F/2 (laboratory), Yamashita and Magalhães (1984) media with Urea (YU), Optimized for Growth (YC) and Optimized for Cost/Benefit (YCB). We saw that the microalgae had better growth with urea as a nitrogen source. The culture medium was optimized, both for growth and for the best cost/benefit, and the experimental validation demonstrated that the empirical model was predictive. The cost analysis showed that the YCB medium represented a 79.4% reduction in the cost of the medium, compared to the F/2 medium. The biomass produced in the YCB medium had a higher percentage of proteins and lipids but did not show differences in the fatty acid profile compared to other media.

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