Effects of Fructus ligustri lucidi

Effects of Fructus ligustri lucidi on the growth, cell integrity, and metabolic activity ogg M.aeruginosa
Abstract
Agricultural waste has been used in the treatment of cyanobacterial bloom because os its environmental friendly and cost-efficient characteristics. In this work, the effects of Fructus lugustri lucidi (FLL) on the growth inhibition, physiological properties, algicidal property, and cell ultrastructure of M.aeruginosa were investigated for the first time. The alga was efficiently inhibited by FLL at the dosages from 0.25 to 4 g/l, and the Chl-a fluorescence and metabolic activity of cells also declined gradually. During 25 days incubation time, the inhibition ratio of 0.25 g/l dosage increased from 8 to 68%, the percentage of intact cells decreased from 94.4 to 59.8%, the inhibition ratio of 2 and 4 g/l dosages was nearly 100%, and the cell membranes were completely broken. The results of Chl-a, propidium iodide (PI) staining, fluorescein diacetate (FDA) staining, and transmission electron microscopy (TEM) assays were consistent with that of growth inhibition tests. The new medium test with the PI staining test suggested that FLL may act as an algicidal agent which can inhibit the growth of M.aeruginosa in the acute time. Consequently, FLL could be an excellent choice in the treatment of eutrophic water.
Introduction
Widespread eutrophication has caused the blooms of toxic cyanobacteria in fresh system. In China, severe cyanobacterial bloom occurred in major lakes almost every year, which have become one of the most serious water pollution problems. Toxic cyanobacteria, mainly M.aeruginosa, are a significant threat to human and environmental health. They can produce hepatotoxin microcystin and neurotoxins, which may lead to headache, fever, abdominal pain, nausea, vomiting, and even cancer. They also deteriorate the quality of drinking water and lead to the destruction of aquaculture and outages of recycled water supply.
Much attention has been given in recent decades to the control and management of cyanobacteria bloom, including reduction of nutrient input, coagulation, clarification, filtration, ozone, and photolysis; however, some of the methods are not applicable to local water. Recently, much effort has been focused on the use of antialgal allelopathy from agricultural waste, which is an environmental friendly, cost-efficiently, and more selectively way. Barley straw, rice straw, soybean straw, wheat straw, and citrus peel have been reported to reduce cyanobacteria populations. In particular, barley straw extracts is confirmed as strong inhibitors, and it has been successfully applied in the treatment of eutrophic water.
Fructus ligutri lucidi (FLL) is the dried and ripened fruit of Ligustrum lucidum, from the family of Oleaceae. It has a wide distribution in Yangtze River basin and southern area of China, i.e., provinces of Hebei, Anhui, and Zhejiang. It also has a long fruiting season which is from July to May of next year. FLL is regarded as Chinese traditional medicine and has anti-inflammatory and anti-cancer properties. It also can be used in cooking in daily life. Every year, a large number of L.lucidum remain unpicked, and the forgotten fruit may be an attractive and inexpensive option for the cyanobacteria control.
To the best of our knowledge, the utilization of FLL for alga inhibition has not been reported in the literature. Thus, FLL was first utilized in the present work for the inhibition of M.aeruginosa.
The main objective of this work was to examine the acute, mid-, and long-term effects of FLL on the cell growth, Chl-a content, metabolic activity, membrane integrity, and microstructure of freshwater M.aeruginosa using flow cytometry (FCM) and transmission electron microscopy (TEM).
Materials and methods
Algal species and cultivation
M.aeruginosa (FACHB-911) was obtained from freshwater algae culture collection at the institute of hydrobiology (China). The cells were cultured in a sterilized Bg11 medium (Allen and Stanier 1968) and were incubated at 250C in 250-ml Erlenmeyer flasks on a 12:12 h light/dark cycle.
Extract of FLL
FLL was obtained from the L.lucidum planted on the campus of Anhui university. FLL was washed thoroughly with deionized water to remove dirt and dried to constant weight at 600C. Then, 20 g of crushed FLL was soaked in 400 ml of ultrapure water and was sterilized with stem for 20 min at 1050C. Finally, FLL was incubated at room temperature for 60 days.
Algal inhibition tests
The inhibition test of FLL was conducted by placing various concentrations of FLL extract (0.25-4 g/l) in 250-ml Erlenmeyer flasks that contained 100 ml of culture medium and 1 ml of algae. Each concentration was in triplicate. The glassware used in the test was sterilized with steam for 20 min at 1050C. The flasks were shaken twice for each 12 h interval and randomly rearranged in the incubator every 2 days. All test groups were cultured dỏ 1 month, and the algal growth was observed and determined at 1, 5, 15, and 25 days.