Screening of isolated lactic acid bacteria as potential beneficial strains for fermented liquid pig feed production

In this paper the selection of potential probiotic strains for producing fermented liquid feed (FLF) for pigs is presented. One hundred and forty six strains of lactic acid bacteria were isolated from ileal digesta of piglets, cecal digesta of slaughter pigs and FLF from a preliminary trial at our laboratory. The strains were identified with repetitive-element PCR and partial 16S rRNA sequencing and screened for acidification potential. Ten of the strains were selected and their culture supernatant was checked for antibacterial activity against Salmonella spp. Also, they were tested in vitro in batch fermentations at 30 °C for 72 h, for their capacity to produce FLF (water:feed ratio of 4:1) with a concentration of acetic acid less than 40 mmol/L and of lactic acid above 100 mmol/L, resulting in a pH below 4.5. The Lactobacillus strains MB 3123 (L. johnsonii), MB 3182 (L. salivarius group) and MB 3083 (L. plantarum) were found to be very effective for the production of FLF. The FLF produced by including this strain had a pH drop from 5.9 to 4.2, 4.3 and 4.4 after 24 h and to 4.1 after 48 h of fermentation. Also, these three strains showed high antimicrobial activity against Salmonella spp. and produced more than 100 mmol/L lactic acid after 48 h fermentation. The MB 3170 strain increased the lactic acid concentration above 100 mmol/L after 48 h, but at 24 h the pH was only 4.5. The results indicate that it is possible to screen for probiotic strains capable of fermenting feeds and of producing high quantities of lactic acid with possible antimicrobial effects in the gastro-intestinal tract of pigs.