TOXICITY OF BISULFITE TO PHOTOSYNTHESIS AND RESPIRATION1

Inhabition of photosynthesis in Chloroccoum sp by bisulfileion was the reciprocal of the light intensity curve. Respiration was least affected of the bisulfite after endogenous substrate was reduced by incubation in darkness. Maximum areduction in growth occurred with bisulfile treatment at or above optimal growth temperatures. Maximum phytotoxicity correlated with conditions resulting in maximum metabolic activity. The order of toxicity was –H₂SO₃HSO₃^?SO₃.     

Enhanced production of free trans-astaxanthin by oxidative stress in the cultures of the green microalga Chlorococcum sp

Free trans-astaxanthin accumulated in the alga Chlorococcum sp. was markedly enhanced from 3.664 mg g⁻¹ cell dry weight to 5.724 mg g⁻¹ cell dry weight when the culture was supplemented with hydrogen peroxide (0.1 mM) under mixotrophic conditions of growth. After saponification, a total of 7.086 mg astaxanthin per g cell dry weight was achieved. Similarly, in heterotrophic cultures, the total astaxanthin content was increased from 1.034 mg g⁻¹ cell dry weight without H₂O₂ to 1.782 mg g⁻¹ cell dry weight with 0.1mM H₂O₂. Results indicate that hydrogen peroxide effectively induces the formation of free trans-astaxanthin in Chlorococcum sp.     

Proliferation of mammalian cells with Chlorococcum littorale algal compounds without serum support

In recent years, serum-free medium for mammalian cell cultivation has attracted a lot of attention, considering the high cost of production and environmental load involved in developing the conventional animal sera. The use of alternative growth-promoting products in mammalian cell cultivation such as extracts from microalgae has proven to be quite beneficial and environmental-friendly. This research aims to cultivate mammalian cells with growth-promoting factors derived from Chlorococcum littorale. We have established a simple extraction using the ultrasonication method and applied the extract in place of serum on mammalian C2C12 cell lines, 3T3 cell lines, and CHO cell lines to compare and analyze the effectiveness of the extract. Cell passage was conducted in a suspended culture condition with the addition of the extract. The results indicate that the extract from microalgae shows a high proliferation rate in all cell lines without fetal bovine serum. Moreover, it is eco-friendly and has huge potential to replace the traditional cell culture system. It could be applied in the fields of regenerative medicine, gene/cell therapies, as well as cultured meat production.     

Chlorococcum sp.混养过程碳氮调控对累积类胡萝卜素和脂肪酸成分影响研究

在BG-11培养液的基础上,选择不同的乙酸钠和硝酸钠浓度组合培养绿球藻Chlorococcum sp.,分析培养过程中干重、类胡萝卜素、总脂及脂肪酸成分,完成Chlorococcum sp.生长及油脂积累的评价。实验结果表明,外源碳源乙酸钠对Chlorococcum sp.的生长和油脂积累有很好的促进作用。乙酸钠和硝酸钠浓度分别为2g/L和1g/L条件下,Chlorococcum sp.培养16天后生物质产率高达276.19mg/(L·d),同时类胡萝卜素和总脂的产率也分别高达1.347mg/(L·d)和108.59mg/(L·d),高附加值脂肪酸二十碳五烯酸(EPA)与二十二碳六烯酸(DHA)占脂肪酸总量也超过了1.5%。     

Composition and biosynthetic pathways of carotenoids in the astaxanthin-producing green alga Chlorococcum sp.

The composition of the secondary carotenoids in the astaxanthin-producing green alga Chlorococcum sp. was analyzed. Eight types of carotenoids were identified by a variety of spectroscopic techniques. Canthaxanthin, 3-hydroxyechinenone, adonirubin and adonixanthin comprised, respectively, 32%, 23%, 12% and 9% of total carotenoids. The results imply that Chlorococcum sp. synthesized astaxanthin from -carotene through various pathways which are different from other astaxanthin-producing microorganisms.     

CELL WALL CHEMISTRY AND ULTRASTRUCTURE OF CHLOROCOCCUM OLEOFACIENS (CHLOROPHYCEAE)1,2

Cell walls of Chlorococcum oleofadens Trainor & Bold were examined ultrastructurally and chemically. The wall of zoospores has a uniform 30 nm width and a regular lamellar pattern. Zoospores and young vegetative cell walk exhibit periodicities, consisting of 20 nm ridges on the outer layer. Vegetative cell walls have a variable thickness of Up to 800 nm and are composed of multiple layers of electron dense material. Further, vegetative walk contain a microfibrillar material composed predominantly of glucose and presumed to be cellulose. Except for this cellulose, vegetative cell wall chemistry is very similar to that of Chlamydomemas being composed of glycoprotein rich in hydroxyproline. The hydroxyproline in Chlorococcum walls is linked glycosidically to a mixture of hetrooligosaccharides composed of arabinose and galactose, and in one instance, an unknown 6-deoxyhexose. Altogether, the glycoprotein complex accounts for at least 52% of the wall. The amino acid composition of the walls is stikingly similar to those of widely different plant species. Indirect evidence indicates zoospore cell walls are also chemically similar to those of Chlamydomonas, and like them, are cellulose free. Thus a major chemical difference between zoospore and vegetative cell walk of Chlorococcum is the presence of cellulose in the latter. The contribution of this microfibrillar cellulose to the physical properties of the vegetative wall is discussed.     

Ketocarotenoid production by a mutant of Chlorococcum sp. in an outdoor tubular photobioreactor

A mutant, MA-1, of Chlorococcum sp., grown in batch culture, produced about 54 mg ketocarotenoids/l with 10 mM nitrogen. The accumulation rate of these ketocarotenoids was independent of the nitrogen concentration under sunlight illumination. Fed-batch cultures showed poor growth and the average productivity of ketocarotenoids dropped from 2.6 mg/l day to 1.6 mg/l day in the two consecutive fed-batch runs.     

MITOSIS AND CLEAVAGE DURING ZOOSPOROGENESIS IN SEVERAL COCCOID GREEN ALGAE1

The fine structure of mitosis and cleavage in Axilosphaera vegetata Cox & Deason, Chlorococcum echinozygotum Starr, Chlorosarcinopsis eremi Chantanachat & Bold, Nautococcus mammilatus Korshikoff, N. terrestris Archibald, N. soluta Archibald, Neospongiococcum solitarium Deason, and Tetracystis aeria Brown & Bold was observed. All possess a phycoplast, but differences in basal body position during mitosis were observed. Nautococcus mammilatus differs from the others as protoplast rotation occurs in many cells prior to cleavage.