Saccharified water hyacinth hydrolysates (acid and enzyme hydrolysate) were used for the efficient production of poly (3-hydroxybutyrate) (PHB) via the Cupriavidus necator bacteria. The bacterium significantly utilizes the enzymatic hydrolyzate which gave the maximum PHB concentration (4.3 +/- 0.4 g L-1), this was greatly exceeded the value of 2 +/- 0.1 g L-1 obtained from the acid hydrolysate amended media. Moreover, for the optimal PHB production. response surface methodology was used through central composite rotary design method which gave improved PHB concentration in microbial cells. After 72 h, 35 g L-1 of reducing sugar contained water hyacinth hydrolysate and 1.5 g L-1 of (NH4)(2)SO4 supplementation in laboratory scale fermentor gave 12 g L-1 of dry cell weight and 7 g of PHB. The produced PHB was characterized under FTIR. GPC and DSC instruments to find out the number average molecular mass, polydispersity index and melting temperature were 1.7 x 10(5) kDa, 1.9 and 170 degrees C respectively. (C) 2012 Elsevier Ltd. All rights reserved.