| This paper is mainly focus on the modification of konjac glucomannan(KGM)with mannanase and monochloroacetic acid. The relationship between the molecular weight of KGM and the time of enzyme-catalyzed degradation,the preparation of carboxymethyl glucomannan(CMKGM) were studied.We also evaluated the cytotoxicity of CMKGM in vitro. We studied the relationship between the moisture-absorption and moisture-retention capacity of CMKGM and different molecular weight and degree of substitution(DS), and screened the best moisture-retention capacity of CMKGM.In the enzyme-catalyzed degradation of KGM, the effects of reaction conditions on enzyme activity were studied.The result shows that the optimum temperature is 50℃and the optimum pH is about 5.4. The mannanase possesses high activity with medium containing enthanol less than 10%(V/V),little activity with medium containing enthanol more than 20%(V/V). The time of enzyme-catalyzed degradation is the most important factor,then the quantity of enzyme,temperature,pH,the concentration of KGM. According to the data of the intrinsic viscosity of KGM and its weight-averaged molecular weight,Mark-Houwink equation can be described as follows: [η]=5.3×10-2Mw0.69.The reciprocal of molecular weight is linear change with the time of enzyme-catalyzed degradation.In the CMKGM preparation section,with the indicators of DS andη, the optimum laboratory conditions preparation of a certain molecular weight of the high DS of CMKGM: reaction time (5～6) h, the theory of the degree of substitution (2～3), the molar ratio of monochloroacetic acid to Sodium hydroxide (2:1～3:1),the reaction temperature (55～65)℃, liquid ratio (10:1～12:1)mL/g, containing enthanol (50～70) %( V/V). The prime factors which selected by means of Confounded Fractional Factorial designs is the theory of the degree of substitution, the molar ratio of monochloroacetic acid to sodium hydroxide,containing enthanol. With response surface analysis,a regression equation about degree of substitution of carboxymethyl was obtained: Y=0.761933+0.052013×X1+0.004675×X2+0.007263×X3-0.038692×X1×X1-0.006075×X1×X2 -0.0 0785×X1×X3-0.130067×X2×X2+0.002225×X2×X3 -0.019392×X3×X3 [X1: the theory of degree ofsubstitution, X2:sodium hydroxide and monochloroacetic acid molar ratio, X3:containing enthanol ( V/V)] CMKGM infrared spectra shows: during carboxymethyl reaction process, primary structure of CMKGM has not changed;deacetylation reaction occurred.Adopting different DS, different concentrations of CMKGM, the cytotoxicities of CMKGM were tested in vitro. Test shows: the cytotoxicity gradation of each group was at 1 grade,no significant cytotoxicity. Orthogonal test showed DS had more important roles in cell activity than concentration of CMKGM. Two factor analysis of variance showed the concentration of CMKGM was significant impact in cell's activity, DS was not significant. A series of CMKGM with different concentration and DS were investigated on their moisture-absorption and moisture-retention properties.CMKGM-III-3 had the highest moisture absorption rate: 27.17% (R.H. 43%). 47.13% (R.H.81%), better than HA,CMKGM- I-3 had the highest moisture rate: 218.29% (R.H. 43%), 43.13% (silica),more effective than HA.pH stability of CMKGM-I-3 and its compatibility with surfactant, stimulation to skin were tested.The results showed CMKGM-I-3 had small changes in viscosity during pH from 4.5 to 10,good solubility with the anionic, non-ionic, amphoteric surfactants. The integral of experimental acute skin irritation and repeated skin stimulation experiments were less than 0.5, without irritation. |
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