Removal of sediment mud of lake and sea bottom and bioconversion to the biodegradable plastic using self-flocculated photosynthetic bacteria

针对污泥的净化和污泥生物转化为生物可降解塑料，首先对污泥进行了化学分析。沉淀泥中有机物含量为5%，海声含量为95%，含大量含磷化合物，泥浆悬浮液（200 g/l人工海水）在30℃条件下厌氧消化7天，释放出约2 g/l的乙酸和约20 mg/l的磷酸离子。利用该厌氧消化液，在30℃厌氧光照条件下（10 klux照度）进行光合细菌培养，培养3天后，生物量约为3 g/l，磷酸盐几乎被去除。所生产的生物质含有62%（干基）的聚羟基丁酸酯（PHB）。因此，同时净化泥沙和生产PHB的可能性被观察到。在无光照的好氧培养条件下，对新分离的具有自絮凝能力的光合细菌Rhodovulum sp.进行了高密度培养，对厌氧消化液进行了净化。该培养体系在人工消化液（乙酸为碳源）培养750 h后，最大生物量达到42.5 g/l，在好氧条件下PHB含量约为30%。此外，利用几个生化工程常数如生长量和某些特定消耗率进行了计算机模拟。计算结果与实验数据吻合较好。因此，通过这些研究，利用这种自固定光合细菌开发一种新的生物反应器系统成为可能。这表明了污泥净化和同时从污泥中生产生物降解塑料的可能性。

Focusing on the purification of sediment mud and bioconversion of mud to biodegradable plastic, firstly, chemical analyses of sediment mud were carried out. Sediment mud was consisted of 5% organic matters and 95% of sea sund and contained large amount of phosphorous compounds, After anaerobic digestion of mud suspension (200 g/l artificial sea wate) at 30 C for 7 days, ca. 2 g/l of acetic acid and Ca. 20 mg/l of phosphate ion was released into the broth. Using this anaerobic digestion liquor, a photosynthetic bacterial cultivation was carried out under anaerobic light condition (10 klux illumination) at 30 C.After 3 days culture, ca. 3 g/l of biomass was produced and almost phosphate was removed. Biomass produced contained 62% (dry basis) of polyhydroxybutyrate (PHB). Thus, the possibility of simultaneous purification of sediment mud and production of PHB was observed.Furthermore, high cell density culture of a newly isolated photosynthetic bacteria, Rhodovulum sp. which had the sel-flocculating ability was carried out using a new single tower bioreactor system to purify the anaerobic digestion liquor under aerobicculture condition eliminating light illumination. By this culture system, maximum biomass concentration attained 42.5 g/l after 750 hour culture with artifitial digestion liquor (acetic acid was a carbon source) and PHB content was ca. 30% even under aerobiccondition. In addition, a computer simulation was carried out using several biochemical engineering constants such as growth yield and some specific consumption rates. As the results, the estimations were in good agreement with the data obtained by experiments.Thus, a new bioreactor system become possible to develop by these investigations using this self-immobilizing photosynthetic bacteria. This indicates the possibility of the purification of sediment mud and simultaneous production of biodegradable plastic from sediment mud.