Neutral sphingomyelinase are cell membrane-associated
and are important for cell signaling during permeability
barrier repair by enhancing the accumulation of ceramide
(Jensen et al. 2005). It is also detected in bacteria, yeast and
mammalian cells, with great variations in sphingomyelinase
activity among different bacterial strains (Di Marzio et al.
1999). In an in vitro study, ceramide reportedly increased in
keratinocytes that were co-cultured with sonicated cells of
Streptococcus thermophilus (Di Marzio et al. 1999). The
results from our current study showed that strains of lactobacilli and bifidobacteria were able to produce acid and
neutral sphingomyelinase with enzyme activities ranging
from 0.7 to 1.5 mU/mL and 1.4 to 3.9 mU/mL, respectively.
It has been suggested that the increased level of ceramide was attributed to sphingomyelinase (>0.1 mU/mL)
obtained from sonicated cells of Streptococcus thermophilus
(Di Marzio et al. 1999). Thus, it is postulated that the concentration of sphingomyelinase in our strains of lactobacilli
and bifidobacteria may be sufficient to also promote
ceramide production in skin cells, thus improving skin
barrier properties.