Effects of α-amylase and glycerol levels on the composition optimization of poly(β-hydroxybutyrate-co-valerate)/starch blended biodegradable resin analyzed with response surface methodology

Abstract

Response surface methodology was used to analyze the effects of the enzyme level (X2) and glycerol level (X1) on objective attributes [water solubility index (WSI), water absorption index (WAI), and maximum loading (Y3)] of a cornstarch/poly(β-hydroxybutyrate-co- valerate) blended composite. A rotatable central composite design was used to develop models for the objective responses. The experiments were run at barrel temperatures of 160, 160, 165, and 165°C, with a screw speed of 40 rpm and complete feeding (filling ratio = 1). Responses were most affected by changes in X2 and to a lesser extent by X1. Individual contour plots of the different responses were overlaid, and regions meeting the optimal WSI of 8.73%, WAI of 3.94 g of gel/g of dry weight, and Y3 of 304.17 N were established at an X2 of 5.43 g and an X1 of 120.79 mL. These predicted values for the optimal process conditions were in good agreement with the experimental data. © 2010 Wiley Periodicals, Inc.