Acid-producing capacity from sugars and sugar alcohols among Lactobacillus isolates collected in connection with radiation therapy

•The highest acid producing capacity from sucrose, glucose and fructose was seen among Lactobacillus isolated during RT.•Sorbitol was fermented to a higher extent during and post RT, especially among isolates collected during RT.•Lactobacillus isolates fermenting xylitol showed the highest acid -producing capacity during RT.•No statistically significant correlations between stimulated salivary secretion rate and Lactobacillus acid -producing capacity were found. To investigate the acid-producing capacity from sugars and sugar alcohols of oral Lactobacillus collected in connection with radiation therapy (RT) to the head and neck region. Lactobacillus were collected from the tongue, buccal mucosa and supragingival plaque in 24 patients before, during, and after RT. The acid-producing capacity of Lactobacillus isolates (n=211) was analyzed using a colorimetric fermentation test in microtiter plates. Solutions containing 2% sugars (sucrose, glucose, fructose, lactose) or sugar-alcohols (sorbitol and xylitol) were used. After 24h of incubation, bacterial acid-producing capacity was determined as strong (pH6). Data regarding intake frequency of sugar-rich products and products with sugar-alcohols was collected. The highest acid-producing capacity using the sugars was seen for isolates collected during RT. Sorbitol was fermented to a higher extent during and post RT, especially among isolates from plaque. Lactobacillus fermenting xylitol showed the highest acid-producing capacity during RT (p