Revalorisation of vine trimming wastes using Lactobacillus acidophilus and Debaryomyces hansenii

BACKGROUND: Mild acid treatments of vine-shoot trimmings result in the hydrolysis of hemicellulosic sugars that can be utilised by Lactobacillus acidophilus CECT-4179 (ATCC 832) and Debaryomyces hansenii NRRL Y-7426 as carbon sources to obtain food additives. Since the high content of glucose in these hydrolysates reduces the effective bioconversion of xylose into xylitol by D. hansenii, the use of Lactobacillus acidophilus, one of the main probiotic species, allows this problem to be solved by the selective consumption of glucose. In order to use both sugars (glucose and xylose), hemicellulosic vine-shoot trimming hydrolysates can be sequentially fermented by both micro-organisms. RESULTS: It was found that, in the first step, L. acidophilus generated almost exclusively lactic acid (32.7 g of lactic acid L−1, QLA = 1.363 g L−1 h−1, YLA/S = 0.72 g g−1) by homofermentative degradation of sugars (mainly glucose), and in the second step, the remaining hemicellulosic sugars were transformed primarily into xylitol by Debaryomyces hansenii (31.3 g of xylitol L−1, QXylitol = 0.708 g L−1 h−1, YXylitol/S = 0.66 g g−1). Furthermore, L. acidophilus proved to be a strong cell-bounded biosurfactant producer. Cell extracts were able to reduce the surface tension (ST) of PBS in 18 mN m−1 units. Lactobacillus acidophilus cells showed no difference in viability before or after PBS extraction of biosurfactants, achieving values of 0.9 × 109 colony-forming units (CFU) mL−1 in both cases. CONCLUSIONS: These results have made a serious contribution to the re-evaluation of a useless and pollutant residue, producing a wide range of natural food additives. Copyright © 2008 Society of Chemical Industry