Suitability of crude glycerol obtained from biodiesel waste for the production of trehalose and propionic acid

Abstract

Crude glycerol is a major by-product of the biodiesel manufacturing industry. Utilization of this by-product is an area of interest among biotechnologists and chemists. In particular, many thermo-chemical and biological methods are available for the conversion of crude glycerol into useful products. The objective of the present study was to determine the suitability of crude glycerol for trehalose (non-reducing sugar) and propionic acid productions by a food microbe, Propionibacterium freudenreichii subsp. shermanii. It was observed that crude glycerol obtained from biodiesel waste favoured higher yields of trehalose and propionic acid production as compared to pure glycerol. In crude glycerol medium, the maximum trehalose yield (based on substrate consumed) achieved was approximately 6.5 times higher as compared to pure glycerol medium. Similarly, the propionic acid yield obtained in crude glycerol medium was two times higher than in pure glycerol. Thus, this study clearly demonstrated the superiority of crude glycerol medium over pure glycerol medium for the simultaneous fermentative production of propionic acid and trehalose. It was also predicted that due to the presence of KCl in crude glycerol, the trehalose yield based on substrate consumed was increased significantly. It was also observed that 10 g l⁻¹ of crude glycerol was the optimum concentration for fermentative production of trehalose and propionic acid.