Preparation Of Sodium Alginate By Composite Enzyme And Electrospinning Properties

As a kind of marine biomass resources, fibrosis utilization of seaweeds with spinning method, is one of the marine strategic emerging industry in China. Main ingredient of alginate fiber is sodium alginate, and its preparation by biological technology has become the research focus. In this paper, based on the cell wall composition of brown algae, alginate bacteria were screened from microbial system of brown algae in Dalian maritime area. Alginate lyase and cellulase with high eznyme activity were extracted after optimization of culture conditions.After preparation of immobilized enzyme by immobilization technology, sodium alginate was extracted by composite enzymatic method. Functional alginate fiber with nano-tourmaline was prepared by electrospinning method which could release negative air ion sustainably.Alginate degradation strains were screened and identified by the 16 S rDNA sequencing and physiological and biochemical identification, which belong to Providencia rettgeri and Alcaligenes faecalis with 99% homology, and they were named as Providencia rettgeri DL and Alcaligenes faecalis DL, respectively. Effect of various factors of culture conditions on the enzyme activity of the two strains of algae degradation bacteria was investigated with Plackett-Burman method and Response Surface Methodology, the significant factors on the enzyme production were studied and the regression equation was established, the 3D response surface and contour map were drawed, and the optimum culture conditions and enzyme activity extremum were determined.Compared with the enzyme activities obtained from the reaction conditions before optimization, the enzyme activity of alginate lyase is 570.5 U/mL, increasing by 15.6%; the enzyme activity of cellulase is 1303.4 U/mL, increasing by 15.4%. Therefore, the model can truly reflect the actual test results.Complex Enzyme was prepared by employing a single enzyme hybrid approach with the ratio of 2:1. After the precipitation with acetone(60%), the cross-linked enzyme aggregates(CLEAs) were prepared with glutaraldehyde(3%) at 35℃ for 150 min. The CLEAs shows good thermal stability, pH-stability, and excellent reusability and storage performance in comparison with the free enzyme. Sodium alginate was extracted with CLEAs, and the kinetics of enzyme catalyzed reaction was investigated. In addition, effects of temperature and pH on the viscosity and extraction yield of sodium alginate were analyzed. The relationship of substrate concentration and reaction rate was also established. The enzymatic reaction constantmK and the maximum reaction ratemaxv were 86.27 g·L-1 and 0.327 g·L-1·min-1,respectively. According to the comparison of the parameters of sodium alginate extracted with complex enzyme method, cellulase and calcium coagulation-acidification method, the extraction yield of CLEAs and free enzyme can reach more than 40%. The viscosity of sodium alginate was 1.14 Pa·s, and the molecular weight was 3.31×105, which was similar with the calcium coagulation- acidification method, and showed superior quality.After extraction of sodium alginate by complex enzyme method, alginate fiber with the function of sustainable release negative air ions(NAI) was spinned using electrostatic spinning method by adding polyvinyl alcohol and nanometer tourmaline. The alginate fibreobtained good surface morphology with the volume ratio of 4/96(w/v) SA solution and 10/90(w/v) PVA solution 1:1, the spinning voltage 25 kV, spinning rate 0.5 m L/h and receiving distance 8 cm by adding TUR(6 mg/m L). The diameter of the fiber was 200-500 nm. The NAI releasing quantity can reach 1800-2000 /cm3. Adding nano TUR had little influence upon the infrared spectrogram of SA/PVA. The thermal decomposition temperature is increased by 74.5 ℃, while the carbonization temperature is increased by 25.3 ℃.The thermal stability is also improved.The results also showed that nano tourmaline existed in electrospinning fiber with half and whole cladding coating states. The tourmaline in half coated fiber surface state can release negative ions by direct contact with the water molecules in the air, while tourmaline in the fiber can release negative ions by contact with water molecules absorbed in SA and PVA.The functionality of the fiber was not easily influenced by the falling off of tourmaline particles caused by external force.