Added pentosans in breadmaking: fermentations of derived pentoses by sourdough lactic acid bacteria

One hundred and seventy strains of sourdough lactobacilli were screened for their capacity to grow optimally by using pentoses. Lb. alimentarius M106 and M137, Lb. hilgardii S32, Lb. brevis AM11, Lb. fermentum I4 and Lb. brevis AM8 had a higher cell yield, growth rate and acetic acid production on a mix of arabinose, xylose or ribose and maltose than on maltose as carbon sources. In the cofermentation process, pentoses were preferentially consumed instead of maltose. Pentosan extract was treated with α-L-arabinofuranosidase from Aspergillus niger or endo-xylanase from Bacillus subtilis to produce hydrolysates respectively each of arabinose and xylose. Depending on the type of pentose and other unidentified compounds, hydrolysates specifically substantiated the growth and acetic acid production of sourdough lactobacilli. Sourdough fermentation by Lb. hilgardii S32 with addition of pentosans and endo-xylanase enzyme increased the acidification rate, titratable acidity, acetic acid content and cell yield number. In addition to the well known role in retarding bread staling, pentosans may also be used as sources of pentoses which favour the performances of selected sourdough lactobacilli.