Valorisation of date fruits by-products for the production of biopolymer polyhydroxybutyrate (PHB) using the bacterial strain Bacillus paramycoides

The aim of this research was to study the valorization of the date fruit by-product by conversion of date syrup into biopolymer polyhydroxybutyrate (PHB), based on the metabolic capacity of the bacterial strain Bacillus paramycoides to accumulate PHB from date syrup. Total reducing sugars in date syrup was essayed using 3',5-dinitrosalicylic acid (DNS) and HPLC methods. Bacillus paramycoides was isolated from soil of the botanic garden of Skikda university, Algeria. The accumulated PHB was extracted using chloroform. It was quantified as crotonic acid in concentrated sulfuric acid (H2SO4) by spectrophotometry at 300nm. Date syrup is characterized by high levels of total sugars (79.66 g/L) with 31.86 g/L of total reducing sugars. PHB accumulation reached its maximum (104.3 ug/mL) after 96 h of incubation at pH 7 and temperature 37°C using Tryptophane as the nitrogen source and acid pretreated syrup at a concentration of 8%. HPLC analysis on Aminex HPX-87H showed that the produced PHB from date syrup is characterized by a chromatogram peak with a retention time at 22.5 min.