Development of a Factorial Design To Study the Effect of the Major Hemicellulosic Sugars on the Production of Surface-Active Compounds byL. pentosus

Abstract

Nowadays, there are no studies about the role of the major hemicellulosic sugars on the production of surface-active compounds by Lactobacillus pentosus, although it was demonstrated that the activity of these compounds can be related to the agricultural residue from which they come, as the sugar solutions obtained from different agricultural residues contain different types and ratios of hemicellulosic sugars. Therefore, in this work, an incomplete factorial design was employed to test the relationship between the type and the ratio of hemicellulosic sugars present in hydrolysates from agricultural residues and the activity of surface-active compounds (cell-bond biosurfactants and extracellular bioemulsifiers) produced by L. pentosus. This design allowed us to establish models (that include linear, interaction, and quadratic terms) between dependent and independent variables. The independent variables used and their variation limits were as follows: glucose concentration (0-10 g L(-1)), xylose concentration (5-15 g L(-1)), and arabinose concentration (0-10 g L(-1)), whereas the 13 dependent variables studied were based on the measurement of surface tension and emulsifying capability. After the study, it was found that the emulsifier capacity of extracellular bioemulsifiers produced by L. pentosus increases at high glucose and xylose concentrations, with glucose concentration as the most influential variable in the range studied. However, the increase of glucose in the absence of xylose produced biosurfactants with low surface activity, with, in this case, the xylose concentration as the most influential variable. Taking into account the xylose/glucose ratio, the best results were obtained with xylose/glucose ratios around 1.5-3.5, which can be found in hemicellulosic hydrolysates from trimming vine shoots or grape marc hydrolysates.