Isolation and characterisation of probiotic lactic acid bacteria from Malaysian fermented fish products budu and bosou

Budu (BUM) is mainly produced in Kelantan and Terengganu, while bosou (BO) is an ethnic
fermented food originated from Sabah. These fermented foods are typically consumed as
condiments for flavour enhancement of meals. In the present work, lactic acid bacteria (LAB)
isolated from both fermented fish products were screened in vitro for their probiotic attributes,
following the FAO/WHO guidelines. The acid and bile tolerance, haemolytic, and
antimicrobial activities, as well as resistance against antibiotics were examined. A total of 42
isolates were characterised by a preliminary subtractive screening method (catalase-negative
and Gram-positive cocci/bacilli). Of these, 14 isolates (four isolates from BO and ten isolates
from BUM) could tolerate the high acidic conditions, thus were further tested for other
probiotic characteristics, and molecularly identified by 16S rRNA sequencing. These isolates
demonstrated survival rates above 90 and 50% when exposed to pH as low as 2.5 and 0.3%
bile salts, respectively. These isolates also did not display β-haemolytic properties, and could
retard the growth of all indicator pathogens to varying degrees. Based on 16S rRNA gene
sequence analysis, the BO and BUM isolates were identified as Lactobacillus plantarum and
L. paracasei, respectively, with 98% similarities to the nucleotide sequences existing in the
GenBank database. These findings suggested that LAB isolated from both budu and bosou
could be a promising probiotic potential, hence could be further developed as medicinal
agents.