Genotypical and phenotypical characterization of Apilactobacillus kunkeei NFICC 2128 for high-mannitol scale-up production using apple pulp and sugar beet molasses as fermentable biological side streams

Abstract

A combination of apple pulp (AP) and sugar beet molasses (M), two biological side streams, has been employed for high yield mannitol production. Apilactobacillus kunkeei is a heterofermentative obligate fructophilic lactic acid bacteria species (FLAB) which is evolutively adapted to preferably metabolize fructose than glucose. A. kunkeei NFICC 2128 strain, naturally isolated from Apis mellifera (honeybee), has been genotypical and phenotypically studied in this project for mannitol metabolism, production, and optimization. Furthermore, a mixture of apple pulp and molasses biowastes (2:1) has been used as fermentable substrates to optimize mannitol upscaled production, yield and productivity. Simultaneous fermentation and enzymatic hydrolysis using invertase were needed to achieve maximum mannitol yield. Furthermore, anaerobic, controlled pH (5.2) and 30 °C fermentation conditions, among other tested at 1 L working volume, showed the highest yield of 0.92 g mannitol / g fructosei and a production of 31.95 g/L of mannitol.