Development Of Low-Cost Substrate Carbon Sources And High-Yield Acetobacter Xylinum Strains For Bacterial Cellulose Production

Bacterial 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.In order to lower the high costs of BC production,especially the costs of carbon sources,several new low-cost carbon sources as well as several high-yield strains of Acetobacter xylinum using mutagenesis were developed.Wheat straw and rice straw were hydrolyzed by dilute acid at high temperature.The best conditions of wheat straw hydrolysates was obtained under 1%H₂SO₄,solid/liquid ratio(1:12) for 30 min.And the best conditions of rice straw hydrolysates was obtained under 5%H₂SO₄,solid/liquid ratio(1:12) for 30 min.The hydrolysates contained complex mixture of compounds that retarded the growth of microorganisms which needed several treatment methods for detoxification.The results showed that the detoxification effects using Ca(OH)₂ was much better than that using NaOH for both wheat stalk and rice stalk hydrolysates.The wheat stalk hydrolysates using Ca(OH)₂ treatment as carbon source was good for BC production,the yield of BC reached up to 15.42 mg/mL which improved 50.28%,65.04%,69.88% respectively compared with D-mannitol,saccharose and glucose.And the yield of BC production using rice stalk hydrolysates with Ca(OH)₂ treatment as carbon source was 16.28 mg/mL.Compared with D-mannitol, saccharose and glucose,it improved 49.94%,79.22%,94.03%respectively.However,the detoxification effects using NaOH was much better than that using Ca(OH)₂ in spruce hydrolysates,and the yield of BC reached up to 10.21 mg/mL.Compared with D-mannitol,saccharose and glucose,BC production was improved 47.66%,70.74%and 51.87%respectively.In addition,the effects of Ca²⁺ and Na⁺ for BC production were also investigated and the results showed that certain concentration range of Na⁺ and Ca²⁺ could improve BC production.In our study,several high-yield strains of Aeetobacter xylinum were developed to solve the problem of low-yield BC production,and a high-yield strain was picked out from Acetobacter xylinum strains.In order to further enhance BC production,this strain was also mutagenized by HNO₂ and LiCl.After screening,the yield of BC was largely increased about 30%.Moreover,the effects of initial pH and different medium on BC production were also investigated.