| Abstract [eng] |
The goal of today‘s food industry is not only to ensure food safety and quality but also food production sustainability. Microbial production of mannitol by lactic acid bacteria from bread waste could be an alternative to the chemical production methods, which are expensive and environmentally unfriendly. The aim of this study was to select lactic acid bacteria and to use bread waste as a fermentation medium for biotechnological production of mannitol as well as to evaluate its potential as a sweetener to reduce calorie intake of sweet bakery products. 17 lactic acid bacteria of the genera Lactococcus, Leuconostoc and Lactobacillus were analyzed to investigate their suitability for mannitol production. 6 strains with the highest mannitol 2dehydrogenase activity (0,07–0,24 U/ml) were selected for fermentation experiments. Fermentation of the model fructose-glucose system was performed at the optimum growth temperature for each strain, maintaining pH at 5,0. The highest mannitol concentration (43,47 g/l) was achieved after 72 h with Lactobacillus rossiae GL14 strain. Waste bread potential of being a resource for the production of fermentation medium was investigated by optimization of the conversion parameters of starch from waste bread to glucose. The optimal loading of bread and enzymes (α-amylase and glucoamylase) were determined to obtain the highest glucose yield of 84,35 % bread dry matter or 97,92 % starch. After parameters (pH and enzyme loading) for glucose isomerization to fructose were optimized, the glucose-fructose syrup with a 1,4:1 ratio was obtained. When produced glucose-fructose syrup was used for biotechnological production of mannitol, mannitol concentration of 20,4 g/l and 36 % yield were obtained. Adjusted fructoseglucose ratio (2:1) in syrup, the addition of corn steep solids, manganese sulfate and soy peptone had a positive effect on growth of Lb. rossiae GL14 and increased mannitol concentration up to 72,98 g/l, yield – up to 51 %. 25 % sugar replacement with mannitol in cupcakes reduced sugar calorie intake by 10 %, the taste and aroma of these cupcakes as well as the overall acceptance to customers were improved. The shelflife studies showed that after 12 days of storage in polyethylene packaging, moisture and texture parameters of these cupcakes remained higher, therefore the shelf-life could be longer than control ones without mannitol. |
