Effect of additives on shelf-life of suspension of photosynthetic bacteria tested using full factorial experimental design

Abstract

This study aimed to investigate the effects of additives, seeking to extend longevity of a viable cell count (>106 CFU/mL) of Ectothiorhodospira shaposhnikovii during storage at room temperature (30±2oC). E. shaposhnikovii were cultured in a 1000L-fermenter until the viable cells reached 4.85±0.50×106 CFU/mL. Afterward, samples were stored in 1L translucent cylindrical plastic bottles for 60 days. Effects of glycerine (0, 0.15%), Na2HPO4·2H2O (0, 0.5 g/L), and Na2CO3 (0, 0.5 g/L) on viable cells were investigated in a full factorial experimental design. Na2CO3 had significant effect and maintained viable cells at 2.35±0.120×106 CFU/mL (a survival rate of 48.4%) and at 1.15±0.057×106 CFU/mL (a survival rate of 23.7%) after 45 and 60 days, respectively. In contrast, glycerine negatively affected the viable cells of E. shaposhnikovii, reducing the counts to 0.037- 0.255×106 and 0.028-0.128×106 CFU/mL after 45 and 60 days, respectively. This indicates that Na2CO3 can be used as a lowcost additive to extend the storage shelf life of E. shaposhnikovii in commercial stage.

Keywords

• ectothiorhodospira shaposhnikovii
• additives
• viable cell
• full factorial experimental design