Study On The Process Of Microbial Degumming And Bio-chemical Combined Degumming Of Hemp Fiber

With the development of the textile industry and the improvement of human consumption,people have higher requirements for ecological and environmentally friendly natural fiber textiles.Because of its many excellent properties,hemp fiber has become more and more popular.However,hemp fiber has low content of cellulose and high contents of pectin and lignin,so degumming is difficult.The length of single hemp fiber is uneven,and the degree of fiber aggregation is high.The length of hemp raw hemp fiber is the shortest among hemp fibers,so it is too difficult to weave,and the requirements for degumming are also higher.This subject has studied the degumming technology of hemp fiber by microbial method,alkaline oxygen one bath method and bio-chemical combined degumming method.Several degumming processes were compared to select the optimal degumming process for hemp fiber.The specific research is as follows:(1)Research on microbial degumming technology.Bacterial samples were collected from soil samples for planting hemp.Five hemp degumming bacteria samples were separated through primary screening and re-screening.After 16S rDNA sequencing results and phylogenetic tree analysis,five bacterial samples were obtained.The strains were as follows:B1 was closely related to Sphingobacterium.B2 and B4 were closely related to Aeromonas salmonicida.B3 was closely related to Pseudomonas.B5 was closely related to Acinetobacter calcoaceticus.These five strains were studied on the degumming process through single factor research and orthogonal optimization experiment.It was concluded that the degumming process of hemp fiber adopted B2,B3 and B5with a compound ratio of 1:1:1,inoculum 15%,pH 7,30?,3 days,bath ratio 1:60,rotating speed180 r/min.The degumming weight loss rate reached 12.82%%.In addition,seven species of Bacillus species were selected for degumming research.The degumming process adopted Bacillus macerans,Bacillus circulans and Bacillus subtilis with a compound ratio of 1:1:1,inoculum 15%,pH 4.5,37?,3 days,bath ratio 1:60,rotation speed 180 r/min.The degumming loss rate reached to 13.53%.Relatively speaking,the degumming effect of Bacillus strains was better than that of hemp degumming strains,but none of them met the requirements of degumming.(2)Research on alkaline-oxygen one-bath degumming technology.The effect of the concentration of NaOH and H₂O₂ and time in the alkaline-oxygen one-bath degumming process were discussed.When weight loss rate,residual contents of pectin and lignin,fiber length and whiteness were taking as evaluation indicators,the alkaline-oxygen one-bath degumming process were studied through single factor research and response surface analysis.The optimal process conditions for alkaline oxygen one-bath degumming were obtained:NaOH 5 g/L,H₂O₂ 5 g/L,Na₂SiO₃ 1 g/L,1 h,98?,bath ratio 1:20.Under the optimal technology,the weight loss rate of hemp fiber was 25.97%,The residual contents of pectin and lignin were 2.34%and 2.65%,respectively.The whiteness and fiber length were 19.56 and 48.77 cm.These results met the industry's degumming requirements.(3)Research on combined degumming technology.Two combined methods of microbe-chemical and microbial-biological enzymes were discussed.The degumming rate and residual contents of pectin and lignin were used to characterize the degumming effect of the hemp fiber.The COD value of the residual liquid was used to characterize the impact of the degumming process on the environment.The surface morphology of the hemp fiber after degumming was observed by scanning electron microscopy.The results showed that the combined microbial-chemical degumming process was:microbial degumming(Bacillus species degumming process)?alkaline oxygen one-bath degumming.The process conditions of one-bath alkaline-oxygen degumming in the combined degumming were:NaOH 3 g/L,H₂O₂ 3 g/L,Na₂SiO₃ 1 g/L,98?,1 h,bath ratio1:20.After degumming,the weight loss rate of hemp fiber was 24.56%.The residual contents of pectin and lignin were 2.51%and 2.84%,respectively.The whiteness reached to 24 and the fiber length was 43.98 cm.The combined microbial-biological enzyme degumming process was:microbial degumming(Bacillus species degumming process)?biological enzyme degumming.The biological enzyme degumming process conditions were as follows:the compound ratio of laccase and xylanase was 2:1,and the concentration of enzyme was 10 g/L,pH 5.5,50?,6 h,bath ratio 1:20.After the combined degumming,the weight loss rate of hemp fiber was 17.02%.The contents of pectin and lignin were 4.26%and 3.18%,respectively.The comparison of several degumming processes showed that the microbial-chemical combined degumming effect was the best.And there were more single fibers.The surface of the microbial-chemical combined degummed fiber was smooth,less gelatinous and the spinnability was good.It's COD value was the lowest(1220 mg/L).It was the most environmentally friendly.