Effects of intermediate metabolite carboxylic acids of TCA cycle on Microcystis with overproduction of phycocyanin

Abstract

Toxic Microcystis species are the main bloomforming cyanobacteria in freshwaters. It is imperative to develop efficient techniques to control these notorious harmful algal blooms (HABs). Here, we present a simple, efficient, and environmentally safe algicidal way to control Microcystis blooms, by using intermediate carboxylic acids from the tricarboxylic acid (TCA) cycle. The citric acid, alphaketoglutaric acid, succinic acid, fumaric acid, and malic acid all exhibited strong algicidal effects, and particularly succinic acid could cause the rapid lysis of Microcystis in a few hours. It is revealed that the Microcystis-lysing activity of succinic acid and other carboxylic acids was due to their strong acidic activity. Interestingly, the acid-lysed Microcystis cells released large amounts of phycocyanin, about 27-fold higher than those of the control. On the other hand, the transcription of mcyA and mcyD of the microcystin biosynthesis operon was not upregulated by addition of alpha-ketoglutaric acid and other carboxylic acids. Consider the environmental safety of intermediate carboxylic acids. We propose that administration of TCA cycle organic acids may not only provide an algicidal method with high efficiency and environmental safety but also serve as an applicable way to produce and extract phycocyanin from cyanobacterial biomass.

Combined Effect of Spirulina Platensis and Punica Granatum Peel Extacts: Phytochemical Content and Antiphytophatogenic Activity

“…These contents are also higher than those found in other Spirulina strains [34,35]. Amongst others proteins, phycocyanin is a blue coloring agent applied in the food industry and cosmetics, stands out with a well-established antioxidant capacity [36].…”

Biodiesel-Derived Glycerol Obtained from Renewable Biomass—A Suitable Substrate for the Growth of Candida zeylanoides Yeast Strain ATCC 20367

“…Cultivated on pure glycerol, C. zeylanoides biosynthesized up to 15.66 g/L of succinic acid after 163 h of cultivation (Table 4). In our case, for the succinic acid biosynthesis by C. zeylanoides ATCC 20367, glucose was the appropriate substrate for increased concentrations production (Table 5) in a time interval of 75 h. After this interval, the succinic acid production abruptly decreased until the end of the process, a fact that could be explained by its conversion to other intermediates of the TCA cycle, organic acids such as fumaric, malic, or α-ketoglutaric acids [73,74]. Compared with literature, our results after 75 h of cultivating C. zeylanoides ATCC 20367 on media containing glucose were comparable with those achieved by Yuzbashev et al [75], who cultivated a genetically engineered strain of Y. lipolytica on a mixture of glucose and glycerol.…”