Manipulação das condições ambientais em culturas de Kirchneriella contorta: efeitos na fotossíntese e no rendimento de biomoléculas de valor agregado

Abstract

Microalgae are a natural source of valuable products and have the potential to be applied in several productive sectors. Among the wide range of biomolecules that synthesize, carbohydrates, proteins and lipids, including carotenoids, are important in health human. Allied to the potentiality of microalgae as biomolecule producers, we have to its production can occur in areas that do not compete with food production and yet, as photosynthetic beings that are, fix CO2, a greenhouse gas. Given the plasticity physiological of the microalgae, techniques of manipulation of its biochemical composition have been proposals for the increase of biomolecules. In this study we investigated the physiology of microalgae Kirchneriella contorta under different concentrations of copper and in two colors of light (diodes light emitters - LED), red and blue. In a first step, under white light we define a range of copper concentration that would not cause a change in the growth rate and in the second stage, crops grown in these concentrations were exposed to white light (control), blue and red. The population density and rates of growth, photosynthetic parameters (PhytoPAM) and concentration of chlorophyll biomolecules a, carotenoids, proteins and carbohydrates. The results showed that the photosynthetic apparatus was sensitive to changes in the quality of light and the presence of copper. From 1.4x10-8 mol L-1 of Cu2+ there was an increase in non photochemical NPQ dissipation, which led to the overcoming of stress, keeping photosynthetic yields similar to control. Chlorophylls biomolecules a and b, carbohydrates and proteins showed higher productivity in intermediate concentrations of copper in the first 48 h of cultivation under white light. Under light blue and at a concentration of 3.8x10-9 mol L-1 of Cu2+ free there was an increase of 50% in the productivity of carotenoids and carbohydrates and 30% of proteins. Growth rates have always remained similar to control, regardless of light quality or concentration of copper. We have shown that, if supplied in the correct quantity, copper can stimulate productivity of biomolecules, and that this productivity can be magnified by synergism by combination with blue LED. This duo proved to be a great tool for biochemical manipulation and growth of Kirchneriella contorta. This study is a contribution to microalgae biotechnology and understanding of the physiology and effects of copper and blue and red light in the microalgae, K. contorta a fresh water Chlorophyta.