几丁质降解菌的筛选及其降解虾壳废弃物的研究

Screening of Chitin-degrading Bacteria and the Study of Their Efficient Degradation of Shrimp Shell Waste

虾蟹壳废弃物产量的日益增加造成了巨大的资源浪费和严重的环境污染。为了提高虾蟹壳废弃物的综合利用价值,本研究从土壤中筛选出几丁质高效降解菌,并通过单因素试验探究降解虾壳的最佳条件及其对虾壳的降解能力。利用胶体几丁质为唯一碳源,采用平板透明圈法对来源于喀斯特地貌的土壤微生物进行富集、分离和纯化,获得了4株具有几丁质降解活力的菌株:粘质沙雷氏菌Serratia marcescens gxas3、蜡样芽孢杆菌Bacillus cereus gxas5、嗜麦芽糖窄食单胞菌Stenotrophomonas maltophilia gxas7以及水生几丁质降解菌Chitinilyticum aquatile gxas1。其中C.aquatile gxas1在96 h时达到最大粗酶活力0.244 U/mL,优于其他3株菌株。利用单因素试验探究C.aquatile gxas1降解虾壳废弃物的能力,并优化其培养基和培养条件,最终确定最佳产酶培养基为果糖2 g/L、KH_(2)PO_(4) 0.7 g/L、K_(2)HPO_(4) 0.3 g/L、MgSO_(4)·6H_(2)O 0.6 g/L、酵母粉0.5 g/L、牛肉膏4 g/L、蛋白胨4 g/L。最佳发酵条件为接种量2.0%、pH值8.0、温度20℃、发酵时间9 d。在最佳发酵条件下,C.aquatile gxas1对虾壳废弃物达到最大降解率60%,其中脱蛋白率为76.77%,几丁质回收率为87%。该研究为微生物降解虾蟹壳废弃物提供了重要的理论依据。

The increasing production of shrimp and crab shell waste has caused huge waste of resources and serious environmental pollution.In order to improve the comprehensive utilization value of shrimp and crab shell waste,this study screened chitin-degrading bacteria from soil,and explored the optimal conditions for degrading shrimp shells and the degradation ability of shrimp shells through single factor experiments.Using colloidal chitin as the sole carbon source,the soil microorganisms derived from karst landform was enriched,separated and purified by plate transparent circle method.Four strains with chitin-degrading activity were obtained:Serratia marcescens gxas3,Bacillus cereus gxas5,Stenotrophomonas maltophilia gxas7 and Chitinilyticum aquatile gxas1.Among them,C.aquatile gxas1 reached the maximum crude enzyme activity of 0.244 U/mL at 96 h,which was better than the other three strains.The ability of C.aquatile gxas1 to degrade shrimp shell waste was investigated by single factor experiment,and its medium and culture conditions were optimized.Finally,the optimal enzyme production medium was determined to be fructose 2 g/L,KH_(2)PO_(4)0.7 g/L,K 2HPO_(4)0.3 g/L,MgSO_(4)·6H_(2)O 0.6 g/L,yeast powder 0.5 g/L,beef extract 4 g/L,peptone 4 g/L.The optimum fermentation conditions were inoculation amount of 2.0%,pH value of 8.0,temperature of 20℃and fermentation time of 9 d.Under the optimal fermentation conditions,the maximum degradation rate of C.aquatile gxas1 shrimp shell waste reached 60%,the deproteinization rate was 76.77%,and the chitin recovery rate was 87%.This study provides an important theoretical basis for microbial degradation of shrimp and crab shell waste.