Production of mannitol usingLeuconostoc mesenteroides NRRL B-1149

Isolation, characterisation and exploitation of lactic acid bacteria capable of efficient conversion of sugars to mannitol

The demand for sugar reduction in products across the food and beverage industries has evoked the development of novel processes including the application of fermentation with lactic acid bacteria. Heterofermentative lactic acid bacteria (LAB) are diverse in their ability to utilise fermentable sugars and can also convert fructose into the sweet tasting polyol, mannitol. The sourdough microbiota has long been recognised as an ecological niche for a range of homofermentative and heterofermentative lactic acid bacteria. A leading determinant in the biodiversity of sourdough microbial populations is the type of flour used. Ten non-wheat flours were used and back-slopped for 7 days resulting in the isolation of 52 mannitol producing isolates which spanned six heterofermentative species of the genera Lactobacillus, Leuconostoc and Weissella. Assessment of mannitol productivity in fructose concentrations up to 100 g/L found Leuconostoc citreum TR116, to have the best mannitol producing characteristics, consuming 95% of available fructose and yielding 0.68 g of mannitol per gram of fructose consumed which equates to the maximal theoretical yield. Investigation of the effects of initial pH on mannitol production and other fermentation parameters in the isolates found pH 7 to be best for isolates Lactobacillus brevis TR052, Leuconostoc fallax TR111, Leuconostoc citreum TR116, Leuconostoc mesenteroides TR154 and Weissella paramesenteroides TR212, while pH 6 was optimal for Leuconostoc pseudomesenteroides TR080. The fermentation of apple juice with each isolate resulted in sugar reduction ranging from 30.3-74.0 g/L (34-72%). When apple juice fermentation with Leuconostoc citreum TR116 was scaled up to 1 L bioreactor a reduction in sugar of 98.6 g/L (83%) was achieved along with the production of 61.6 g/L mannitol. This demonstrates a fermentative process for sugar reduction in fruit juice with concomitant production of the sweet metabolite mannitol to create a fermentate that is suitable for further development as a low sugar fruit juice alternative.

Effects ofBacillus subtilisandLeuconostoc mesenteroideson the Quality Characteristics of PotatoGaraetteok

To investigate the texture and cooking properties ofgaraetteokelaborated with potato flour, experimental products were elaborated replacing partially the rice flour, traditionally used, with nonfermented (NF) or fermented potato flour withBacillus subtilis(BS) orLeuconostoc mesenteroides(LM) in percentages of 15% (NF15, BS15, and LM15) and 20% (NF20, BS20, and LM20). The control product (CON) was made using only rice flours. The pH ofgaraetteokwas significantly lower in the BS and LM groups compared to CON and NF. Titratable acidity was the highest in BS20 and LM15. LM groups showed similar textural profiles to CON. The addition of potato flour togaraetteokincreased the turbidity of soup (tteokguk), but the fermentation significantly lowered its turbidity. During storage for 24 h,garaetteokwith fermented potato flour showed the inhibition of starch retrogradation. All scores of LM15 and LM20 were better than other potatogaraetteoksand similar to those of CON with the exception of color acceptance. Consequently,garaetteok-added potato flour fermented withL. mesenteroideswas the most preferable in terms of texture, cooking, and sensory characteristics.

Characterization of the microbial diversity in yacon spontaneous fermentation at 20 °C

The prebiotic fructooligosaccharide content of yacon makes this root an attractive alternative for the supplementation of a variety of food products. The preservation of yacon by fermentation has been proposed as an alternative to increase the probiotic content of the root concomitantly with its shelf life. Thus the fermented yacon could have significant functional content. The objective of this research was to characterize the biochemistry and microbiology of spontaneous yacon fermentation with 2% NaCl and define the viability of the proposed process. The biochemical analysis of spontaneous heterolactic fermentation of yacon showed a progressive drop in pH with increased lactic and acetic acids, and the production of mannitol during fermentation. The microbial ecology of yacon fermentation was investigated using culture-dependent and culture-independent methods. Bacterial cell counts revealed a dominance of lactic acid bacteria (LAB) over yeasts, which were also present during the first 2 days of the fermentation. Results showed that the heterofermentative LAB were primarily Leuconostoc species, thus it presents a viable method to achieve long term preservation of this root.