Study On The Algal Inhibition Effect Of Plant Polyphenols And Algal Cell Physiological Characteristics Treated By Them

In this study, plant polyohenols, as a natural plant secondary metabolite, were applied to control excessive growth of harmful algae. Hierarchical Cluster Analysis (HCA) was performed to devide the polyphenols into several groups. The polyphenols with higher inhibition efficiency were examined deeply on Microcystis aeruginosa, including the dose-response relationship, inhibition kinetics, inhibitory factors, the changes of plant polyphenol's concentration and intracellular organism. The algal physiological character was observed including the structure of cells morphology, the activity of intracellular protease, the concentration of non-enzyme material, and cells activity during the treatment. And plant polyphenols were added into the actual water samples containing algae to obtain the algicides'inhibition percentages and effects on water quality.The results showed that,19 different plant phenols were devided to four groups. The highest inhibitory group included p-HBA, EA, HQ, TC, CAT and GEA. GA, FA, PCA and RUT were belonged to the higher inhibitory group. SIA and VA were classified to the third group. The fourth group contained PHL, RES, SYA, HHQ and SAA, which demonstrated no effects on or less stimulated to the algal growth. By the comparison of EC50, the strongest inhibitory activity compound was Hydroquinon, followed by Catechol,ρ-Hydroxybenzoic acid, Gentisate, Caffeic acid, Ellagic acid and Tannic acid. When EC40-EC60 concentration of plant polyphenols were added into algal solution with 4-6×109cell/L algal density, the algal biomass would experience a slow or suspended growth phase for 5-7 days. The concentration of plant polyphenols would be reduced in 2 days to avoid secondary pollution.In this study, the combination form of polyphenols played as an important role in algal inhibition. The research showed that mixture with Catechol had a stronger inhibitory activity, while Gentisate would weaken the anti-algal activity. Algicide with equal toxic unit of Hydroquinon, Catechol andρ-Hydroxybenzoic acid had played the strongest effect on algal inhibition. Cell initial density was also an important factor for inhibiting the algal grow.The paper focused on the variation of MCLR and release of intracellular organism during the inactivation of algae. The concentration of total MCLR treated by EC90 polyphenols rapidly increased in 24h, which was more than twice the concentration of control sample, causing a release of mounts of MCLR to solution. After 7 days, the concentration of extracellular MCLR was reduced to less than 2μg/L. The intracellular organism including aromatic protein-like substances, microbial byproduct-like material and UV fulvic acid-like compounds were also released into solution and degraded gradually.When was exposed to plant polyphenols, the algal cell membrane was impaired, the cell permeability turned worse, and wrinkle and depressed cells appeared. When the concentration of CAT was below 0.8mg/L, the activity of apoenzyme enhanced, and the concentration of non-enzyme substance increased in 2 days to maintain the normal exchange of materials and energy. While more of CAT was added to solution, that could cause the damage and death of algal cell.The paper also used plant polyphenols to treat the actual water with green algae, and the water quality was little affected during treatment.