title: Influence of chitosan-sodium alginate pretreated with ultrasound on the enzyme activity, viscosity and structure of papain.
abstract: BACKGROUND
  Ultrasound treatment has been shown to be an effective technique for improving the activity of immobilized enzymes. However, its mechanism is unclear.
  
  
  RESULTS
  The effect of ultrasonic pretreated chitosan-sodium alginate (CHI-ALG) on the enzymatic activity of papain was investigated via a single factor (temperature, time, frequency, power) experiment. The maximum relative enzyme activity of papain was observed when it was mixed with ultrasound pretreated CHI-ALG at 135 kHz, 0.25 W cm-2and 50 °C for 20 min, during which the relative activity increased by 72.14% compared to untreated CHI-ALG. Viscosity analysis of papain mixed with CHI-ALG pretreated and untreated with ultrasound revealed that stronger association interactions between the polymers were formed compared to the untreated sample. Fluorescence and circular dichroism spectra indicated that the ultrasonic pretreatment of CHI-ALG increased the number of tryptophan on the papain surface and also increased the content of α-helix by 6.97% and decreased the content of β-sheet by 3.45% compared to the untreated solution.
  
  
  CONCLUSIONS
  The results of the present study indicate that papain combined with CHI-ALG pretreated with the appropriate ultrasound could be effective technique for improving the activity of immobilized enzymes as a result of changes in its structure and intermolecular interactions. It is important to extend the application of CHI-ALG gel in the immobilized enzyme industry. © 2016 Society of Chemical Industry.
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health (BTBU), School of Food and Chemical Engineering, Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology and Business University, Beijing, 100048, China.|Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Key Laboratory of Flavor Chemistry, Beijing Technology and Business University, Beijing, 100048, China.|Beijing Laboratory for Food Quality and Safety, Beijing Technology and Business University, Beijing, 100048, China.
authors.forename: Liping
authors.initials: L
authors.lastname: Feng
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health (BTBU), School of Food and Chemical Engineering, Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology and Business University, Beijing, 100048, China.|Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Key Laboratory of Flavor Chemistry, Beijing Technology and Business University, Beijing, 100048, China.|Beijing Laboratory for Food Quality and Safety, Beijing Technology and Business University, Beijing, 100048, China.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health (BTBU), School of Food and Chemical Engineering, Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology and Business University, Beijing, 100048, China.|Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Key Laboratory of Flavor Chemistry, Beijing Technology and Business University, Beijing, 100048, China.|Beijing Laboratory for Food Quality and Safety, Beijing Technology and Business University, Beijing, 100048, China.
authors.forename: Duoxia
authors.initials: D
authors.lastname: Xu
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health (BTBU), School of Food and Chemical Engineering, Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology and Business University, Beijing, 100048, China.|Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Key Laboratory of Flavor Chemistry, Beijing Technology and Business University, Beijing, 100048, China.|Beijing Laboratory for Food Quality and Safety, Beijing Technology and Business University, Beijing, 100048, China.
authors.forename: Dandan
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health (BTBU), School of Food and Chemical Engineering, Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology and Business University, Beijing, 100048, China.|Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Key Laboratory of Flavor Chemistry, Beijing Technology and Business University, Beijing, 100048, China.|Beijing Laboratory for Food Quality and Safety, Beijing Technology and Business University, Beijing, 100048, China.
authors.forename: Zhenghua
authors.initials: Z
authors.lastname: Huang
mesh_terms: D000464:Alginates / Q000737:chemistry* / Q000528:radiation effects*; D048271:Chitosan / Q000737:chemistry* / Q000528:radiation effects*; D002942:Circular Dichroism; D004800:Enzymes, Immobilized; D020723:Glucuronic Acid / Q000737:chemistry / Q000528:radiation effects; D006603:Hexuronic Acids / Q000737:chemistry / Q000528:radiation effects; D010206:Papain / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D013696:Temperature; D000069453:Ultrasonic Waves; D014783:Viscosity
chemical_list: D000464:Alginates; D004800:Enzymes, Immobilized; D006603:Hexuronic Acids; D020723:Glucuronic Acid; D048271:Chitosan; D010206:Papain
keywords: circular dichroism; fluorescence; papain activity; ultrasonic pretreatment of chitosan-sodium alginate; viscosity