Removal Of Lignin And Protein From Tobacco Stem

The preparation of tobacco flakes by papermaking methods makes discarded tobacco stem reused,which help save resources and reduce environmental pollution.Lignin,which is one of the main components in plants,account for 4%-8% of tobacco stem.The burning of lignin produces phenol,catechol and other phenolic substances,which not only affects the sensory quality of cigarettes,but also endangers human health.Therefore,removal of lignin from tobacco stalks in the process of preparing tobacco flakes by papermaking methods is conducive to improve the quality of tobacco products.Laccase is a non-toxic substance,which can degrade lignin in mild conditions,and therefore it is easy to achieve industrialization.The mechanism on enzymatic hydrolysis of lignin was discussed by using lignin model compounds.The effects of weak alkali pretreatment and surfactants on the enzymolysis by laccase were explored in this work.The optimum process avariables for protease to degrade residual laccase and protein in tobacco stem were also studied.The work has good practical significance for promoting the effective utilization of wasted tobacco stem and improving the quality of recycled tobacco leaves.The mechanism of laccase degradation of dimer lignin model compond was studied.It is found that the nonphenol model compound can not be degraded by laccase while phenolic models can be partially degraded by laccase.Laccase degrades the phenolic model compound by breaking the ?-O-4 linker between the benzene rings.Pretreatment of tobacco stem with NaHCO3 could remove part of the lignin from tobacco stem,the removal ratio was 19.12%.The efficiency of enzymolysis by laccase after pretreatment with NaHCO3 was improved,and lignin removal ratio reached 38.36%.When enzymolysis was carried out first followed by the treatment with NaHCO3,the removal ratio was 29.26%,which indicated that NaHCO3 pretreatment promoted the enzymatic hydrolysis of lignin.The SEM images showed that there were many pores on the surface of tobacco stem after NaHCO3 treatment.Besides,the results of mercury intrusion porosimetry also showed that the surface porosity of tobacco stems was significantly increased after pretreatment with weak alkali.The addition of Tween 80 and PEG 6000 into enzymolysis system promoted the efficiency of enzymatic hydrolysis.Tween 80 and PEG 6000 had the best effect on enzymatic hydrolysis at the concentration of 0.12 g/L,in which lignin removal ratio were 29.78% and 19.51%,respectively.It was found that the effect of Tween 80 on laccase activity was better than that of PEG 6000.The surface activity of Tween 80 is also better than that of PEG 6000.The results from the pilot scale test showed that the smell from lignin was reduced after the enzymatic hydrolysis of tobacco stem.The laccase degradation of lignin resulted in the increase of protein content in tobacco stem,in which increase ratio reached 21.43%.Neutral protease was added to degrade protein,and the optimal process variables for protein removal is as follows:the temperature is 50 ?,pH is 6.0,rotate speed is150 r/min,protein content is 0.4 g/L,reaction time is 4 h.The removal rate of protein reached 31.76%.The addition of PEG 6000 and Tween 80 in enzymatic hydrolysis system promoted the efficiency of enzymatic hydrolysis,the protein removal ratio was 52.94% with the addition of Tween 80 while the protein removal ratio reached 45.88% with the addition of PEG 6000.