| ABSTRACTBacterial cellulose (BC) is one of the most promising biological based materials with broad prospective applications. Compared with other natural plant cellulose, BC displays many unique properties including higher purity, higher crystallinity, higher degree of polymerization, higher water absorption and retaining capacity, higher tensile strength, stronger biological adaptability and so on. Therefore, this kind of material has tremendous economic and societal benefits in different fields, such as artificial skin and vessel, binding agents, loud speaker diaphragms, paper making, textile, composite membranes and so on. However, the problems of the high economic costs of carbon sources and relative low-yield strain become a bottleneck for BC's industrial production and extended applications.To lower the higher costs of BC production, especially the costs of carbon sources, several new low-cost carbon sources were developed, and the influence of calcium cation on the yield of BC under the static environment was investigated as well. Firstly, konjac powder was hydrolyzed by dilute acids (0．5 mol/L sulphuric acid or 1．0 mol/L hydrochloric acid respectively) in boiling water bath for 1 h. And then, the pH value of this hydrolysate solution was adjusted by calcium hydroxide or sodium hydroxide, and alkaline combined with active carbon or laccase respectively for detoxification. The results showed that the detoxification effect using calcium hydroxide was much better than that of using sodium hydroxide for BC production. Besides, if adding active carbon or laccase in the process, the detoxification effects would go further and BC production could be improved more using these hydrolysates.Under same concentration of carbon sources, BC production using these hydrolysates as carbon sources was much higher than that using glucose or mannose. The hydrolysate from konjac powder could reduce the economic cost and improve the yield of BC production, which was very helpful and promising for the possibility of mass industrial production of BC.Secondly, wheat straw, corn stalk and sesame stalk were soaked and saturated by 72% sulphuric acid at room temperature for 4 hours, then diluted by water to 4% acid concentration and further hydrolyzed at 121(?) for 30-60 min. Then, these hydrolysates were detoxified by sodium hydroxide, calcium hydroxide or combined with active carbon or laccase for the supplying of new carbon sources for the BC production. Although these hydrolysates from crop straws were not as good as konjac powder hydrolysate for carbon sources, they did provide a new way for BC production. The effect of Ca cation for BC production and productivity was investigated and the result showed that Caaddition could improve the BC production and productivity in the static culture remarkably under a certain concentration range (0-7mmol/L).This paper also developed several high-yield strains of Acetobacter xylinum using mutagenesis in order to solve the problem of low-yield for BC production. Several methods were utilized, including the method of using 0．025 mol/L nitrous acid (HNO), using 0．25% lithia chloride (LiCl), using 75 (?)mol/L sodium bromide (NaBr) and 15 (?)mol/L sodium bromic acid (NaBrO), using LiCl combined with NaBr and NaBrO, using 30 W ultraviolet radiation (UV), using UV combinated with NaBr and NaBrO, and using LiCl combined with UV and their mutual and synergetic effect. After screening, 3 high-yield strains mutagenized by HNO soakage and 2 high-yield strains mutagenized by LiCl combined with UV were picked out from many strains. By using the screened strains, the yield of BC was improved about 140%, 120%, 180%, 45% and 40% respectively.Kaiyan Qiu (Textile Chemistry and Engineering of Dyeing & Finishing)Supervised by Dr. Feng Hong... |
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