Valuable ingredients and feed toxicity evaluation of Microcystis aeruginosa acidolysis product in mice

This research studied the extraction from Microcystis aeruginosa using hydrochloric acid method as a potentially valuable protein resource from eutrophic lakes. Amino acid composition, residual algal toxins, and heavy metals of the acidolysis product were studied. After 18 h of hydrochloric acid treatment, the product of M. aeruginosa contained 17 amino acids, 51.34% of total amino acid requirements, and 30.25% of the livestock and poultry essential amino acid (Eaa). The residual microcystin-LR (MC-LR) was 0.94 µg kg⁻¹, which was less than WHO drinking water limit of microcystins. The removal ratio of microcystins was higher than 99.99% during the process of hydrolysis. The concentration of heavy metals of the product was in compliance with feed standards. Furthermore, using Horn’s method, Mouse Micronucleus Test and Sperm Shape Abnormality Test were conducted to study the forage safety of the product. Half lethal dose (LD₅₀) of acidolysis product in mice was >9.09 g kg⁻¹ body weight, actually belonging to non-toxic grade. Every dose treatment did not significantly increase activities of alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and γ-glutamyltransferase (γ-GT). The results of both micronucleus test and sperm shape abnormality test were negative, which suggested the product with no mutagenicity and sperm malformation effects. This study indicated that the acidolysis product of M. aeruginosa was safe to be used as a feed ingredient.     

Cryopreservation of a water-bloom forming cyanobacterium, Microcystis aeruginosa f. aeruginosa

A method for the Cryopreservation of Microcystis aeruginosa f. aeruginosa is described. For the five strains tested, dimethyl sulfoxide (DMSO) (3% v/v) was the only effective cryoprotectant for freezing to, and thawing from -196°C and allowed the successful recovery (>50%) of all the strains. The viability of frozen material was independent of the period of storage in liquid nitrogen. The strain NIES-44 (National Institute for Environmental Studies) had a recovery level of greater than 90% at 3–10% (v/v) DMSO in both two step and rapid cooling methods. The other three strains, NIES-87, 88 and 89 had greater than 60% of viability after freeze/thawing in presence of both 3% and 5% DMSO concentrations. On the other hand, the strain NIES-90 showed approximately 50% of viability in only 3% DMSO solution after two step cooling to and thawing from -196°C. This strain was damaged by greater than 4% DMSO and by rapid cooling to -196°C. It was found that cold shock injury and the cytotoxicity of DMSO were different at a strain level.     

Assimilation of different cyanobacteria as food and the consequences for internal energy stores of juvenile roach

Juvenile roach Rutilus rutilus fed on the cyanobacterium Aphanizomenon were able to maintain liver glycogen and muscle protein concentrations. In contrast, internal energy stores of fish fed on the cyanobacterium Microcystis were degraded. Liver glycogen, however, was higher than in starved fish, suggesting that roach was able to obtain some nutrients (probably carbohydrates) from the mucus cover of Microcystis . Weak assimilation of radiolabeled Microcystis by roach was detectable, and assimilation rates increased with increasing proportion of Aphanizomenon in a mixture of both cyanobacteria. It is concluded that the incomplete digestion of Microcystis was the main reason for the negative growth rates of roach when fed on this cyanobacterium species.     

Effect of calcium peroxide on the growth and proliferation ofMicrocystis aerusinosa, a water-blooming cyanobacterium

The potential of calcium peroxide to act as an agent for waterblooming control was investigated by examining the growth inhibition ofMicrocystis aerusinosa. Due to the chemical nature of calcium peroxide, it can remove dissolved phosphate by forming an insoluble precipitate, generating radicals, coagulant, and oxygen as byproducts as it dissolves in water. The growth ofM. aerusinosa was severely inhibited and the chlorophyll-a concentration was drastically decreased in the presence of calcium peroxide. With 200 ppm of calcium peroxide dosage, a chlorophyll-a concentration of 1,700 mg/m³ was lowered to below 10% of its initial concentration after 4 days. One possible explanation for this growth inhibition is the removal of the available phosphate by calcium peroxide.     

氮磷比对有机磷环境中微藻砷代谢的生态风险效应北大核心

【目的】探究了以单酯磷D-葡萄糖-6-磷酸二钠(D-glucose-6-disodium phosphate,GP)为唯一磷源时含砷(As5+)水体中不同氮磷质量比对铜绿微囊藻(Microcystis aeruginosa)生长及砷代谢和微囊藻毒素(microcystins,MCs)释出的影响。【方法】将氮磷饥饿状态的藻细胞于含砷水体中不同氮磷比条件下进行实验,通过测定藻细胞密度(OD680)、叶绿素a(chlorophyll a,Chla)、实际光合产率(Yield)、超氧化物歧化酶(superoxide dismutase,SOD)、砷的存在形态以及微囊藻毒素含量,分析该藻在砷胁迫下的生理响应以及砷代谢机制。【结果】氮磷饥饿状态藻细胞对较高GP水平(0.1 mg/L)下的低氮磷比有更好的适应性,较低GP水平(0.02 mg/L)下的高氮磷比能显著促进培养初期藻细胞的OD680、Chla和Yield;SOD在培养初期与末期受氮磷比影响显著。GP环境下铜绿微囊藻经8 d培养后氮磷比为10:0.1介质中的砷表现为以亚砷酸盐(As^(3+))为主,占水体总砷(total arsenic,TAs)含量的78.8%,其余氮磷比环境中仍以As^(5+)为主,藻体砷形态则均以As^(5+)为主,氮磷比为1:0.1时有机砷占藻体TAs比例最高。藻细胞砷代谢受GP水平影响显著,较高GP环境(0.1 mg/L)下砷的代谢总量也更高,氮磷比为10:0.1时砷代谢以As^(5+)的还原和As^(3+)释出为主,低GP环境下(0.02 mg/L)砷代谢的甲基化水平提高。介质中MCs的含量与GP水平有关,较高GP的低氮磷比水体中MCs含量最低。【结论】研究结果对全面了解有机磷源含砷水体中藻华暴发及砷生态风险的科学管控具有重要意义。     

Methods for prevention of mass development of the cyanobacterium Microcystis aeruginosa Kutz emend. Elenk. in aquatic systems

Methods for prevention of mass development of the cyanobacterium Microcystis aeruginosa Kutz emend. Elenk. in continental water bodies and industrial water supply systems are reviewed. The physicochemical, chemical, and biological methods for prevention of M. aeruginosa development in water bodies and water supply systems are considered; examples of successful inhibition of M. aeruginosa growth in laboratory experiments are demonstrated. The scientific problems are outlined that are to be solved for perfecting techniques for prevention of M. aeruginosa mass development in open water bodies and in closed water supply systems.     

Toxicité du cuivre vis à vis de Microcystis aeruginosa Kütz. et d'Aphanizomenon flos-aquae Ralfs

We studied the toxicity of copper on Microcystis aeruginosa and Aphanizomenon flos-aquae. The toxicity phenomena can be described by the survival dose relationship which allows us to define the three parameters: threshold concentration (Cs), sensitivity (k) and a NL. 50%. The latter corresponds to the copper concentration which reduces the number of cells at the end of the exponential phase by 50%. A. flos-aquae is very clearly less tolerant than M. aeruginosa to copper. Viable cell counts based on electron transport activity showed that M. aeruginosa cultures can detoxify copper.     

A COMPARISON OF MULTIPLE CONTAINER AND TUBULAR SYSTEMS FOR THE LARGE SCALE LABORATORY CULTURE OF UNICELLULAR ALGAE

SUMMARY

It is pointed out that due to its construction a tubular system has many advantages, compared to a multiple container system. The most important being the ease of manipulation and the higher yield of algal material. The tubular system has at least a ten fold higher yield per unit time and volume than multiple container systems.     

EFFECT OF PHOSPHATE CONCENTRATION ON THE FINE STRUCTURE OF THE CYANOBACTERIUM,MICROCYSTIS AERUGINOSA KÜTZ. EMEND. ELENKIN

SUMMARY

Microcystis aeruginosa toxic strain UV-006 stored a fixed amount of polyphosphate in spherical granules located in the centroplasm. Twenty four hours of phosphate starvation induced use of stored polyphosphate, manifested by reduction in granule numbers. Reintroduction of 2, 4 or 8 mg l^?1 K₂HPO₄ resulted in redeposition of polyphosphate in a critical number of centroplasmic polyphosphate granules. Growth rate was unaffected by phosphate concentrations, although the final cell yield was slightly lower at 8 mg l ^?1

Continued starvation decreased photosynthetic rate and growth ceased. Cells appeared senescent. Cyanophycin and polyglucoside reserves apparently increased in these cells, whilst thylakoids were reduced in number and reorientated away from. the cell wall and polyhedral bodies were lost. After the initial decrease, centroplasmic polyphosphate bodies increased to about half of the maximum numbers stored in cells grown in the presence of phosphate, suggesting that translocation of phosphorus from other areas in the phosphate-starved cell occurred.

Two further polyphosphate deposition areas were observed. DNA fibrils may have represented nucleation sites for developing polyphosphate granules. Intrathylakoidal deposits were rare.