Effect of protein hydrolizates on growth kinetics and aminopeptidase activities of Lactobacillus

Bifidobacteria are probiotics microorganism widely used in food industries [1]. They are a nutritionally heterogeneous group, whose growth is often slow or limited on synthetic media lacking of a growth-promoting factor [2]. Although Bifidobacteria are able to use ammonium salts as their only source of nitrogen [3], the supplementation of peptides and amino acids is considered requirement for the economical production of these strains [4]. Lazzi and colleagues [5] demonstrated that also poultry feathers enzymatic hydrolizate could be a suitable nitrogen source for the production of microbial biomass with improved viability. Chemical composition of poultry feathers hydrolizate has revealed that it is poor in free amino acids and is mainly composed by peptides [5]. To deepen this aspect, in this work, the growth performances of poultry feathers hydrolizates on eight Bifidobacterium strains belonging to different species were compared with two commercial hydrolizates, i.e. Tryptone and Peptone. The maximum cell density (ODmax) and the maximum specific growth rate (mmax) were used to determine the nitrogen source preferred by each species tested. Moreover, in order to investigate the effect of the