報告書番号

U02061

タイトル（和文）

微細藻類の機能を用いた排水中からの微量ホウ素除去法

タイトル（英文）

Application of microalgal function for boron removal from waste water.

概要 （図表や脚注は「報告書全文」に掲載しております）

微細藻類機能を排水からのホウ素除去に適用することを目標として、ホウ素除去能力を有する微細藻類の探索を行い、またホウ素除去機構に関する検討を行った。一定濃度以上のホウ素に対して耐性を有し、かつホウ素除去能を持つ微細藻類はこれまでに知られていない。そこで自然環境試料から、ホウ素除去能力を有する微細藻類をスクリーニングし、それらについてホウ素除去能を評価した。その結果、ホウ素除去能力を有する微細藻類を得た。ホウ素除去機構に関する検討では、微細藻類の菌体外多糖類の錯体形成能によりホウ素が除去されていると考えた。そこで錯体形成能の高いマンニトールをモデルとして用いて、ホウ素-マンニトール錯体形成の量的把握を行った。その結果、過剰な糖に対して錯体を形成するホウ素量は相対的に少ないことが示唆された。錯体形成能が高い藻類由来多糖類の解明及びそれを用いた微細藻類のホウ素除去能力向上が次の課題である。

概要 （英文）

Recently, boron has received increasing attention environmental contaminants, leading to more stringent legal regulation. Boron is an essential minor element for plants and is supplied to cultivated land in soil fertilizer. Successful recovery of boron from waste water can satisfy legal requirement, protect the environment, and provide a source of boron for use in fertilizer. Here, we observe strains of microalgae capable of removing boron from waste water streams and evaluate the chelating ability of several sugars.1. Screening of microalgae which shows boron removal ability from solution. We screened microalgal samples for the boron removal ability. Many microalgal samples from natural environments were inoculated into several culture media, and cultured for four weeks under laboratory conditions. After culturing, decreases in the boron concentration of the culture media were observed in several samples. Following repeated culture cycles, two samples showed significant reproducible boron removal from culture media. These almost pure cultured microalgal samples should be investigated for their quantitative ability to remove boron recovery as the next step.2. Basic observation of chemical reaction between boron and sugar compounds. From experimental results and a literature survey, mannitol was identified as the most effective boron chelator known. However, when excess mannitol was reacted with boron and precipitated by ethanol, the ratio of precipitate against total boron in solution was less than 10%. This result indicates that the chelate ability of mannitol is not high enough to account for the boron removal by microalgae, and suggests that the polysaccharide present on these microalgae is of a previously unknown type.

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