Sugar cane juice for polyhydroxyalkanoate (PHA) production by batch fermentation

Abstract

Clarified sugar cane juice was evaluated as an alternative substrate for the batch production of polyhydroxyalkanoates (PHAs) by Alcaligenes latus, and a mineral salt broth was used as the control. The study included the physicochemical characterization of the juice, measurement of the fermentation kinetic parameters and identification of the polymer type by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Batch-type aerobic fermentations were performed (33°C at 200 rpm and pH 6.5-7 for 60 h) and set at 20 gL^-1 of fermentable sugar and a carbon/nitrogen ratio of 28.3/1. A 10% v/v ratio of inoculum/substrate was used. The alternative substrate presented a greater concentration of magnesium and micronutrients such as Fe, B, Zn, Mg and Cu compared to the control. The biomass yield ( ) of the juice was 1.27 g.g^-1 (0.414 g.g^-1 in control medium), which was 69% more than the control medium; the product-substrate yield ( ) was 0.10 g.g^-1, which was similar to the control medium (0.15 g.g^-1 control medium). The production of PHB was of 1.3 gL^-1, less than half of the concentration obtained in commercial substrate. Infrared spectroscopy indicated that the polymer obtained in the evaluated substrates was polyhydroxybutyrate (PHB). The clarified juice of sugar cane, without the addition of nutritional supplements can be used for the production of biomass of A. latus, first step in the production of PHB.

Keywords: Alternative substrate, Alcaligenes latus, polymer, polyhydroxybutyrate (PBH), fermentation.

African Journal of Biotechnology, Vol 13(40) 4019-4027