PoultryUSA - August 2018 - 25
The safety and stability of probiotic strain
Bacillus subtilis DSM 32315 (GutCare ) supports
its commercial application.
Bayo Sokale DVM, PhD and Anita Menconi DVM, PhD. Technical Services Managers, Evonik Industries.
Bacillus subtilis (B. subtilis) is a rod-shaped, Gram-positive bacterium, commonly found in the soil and normal gastrointestinal
tract of humans and animals (Hong, et al., 2009; Chaiyawan,
et al., 2010). It is a facultative anaerobe and historically has
been considered as an obligate aerobe. As with other members
of the genus Bacillus, it is favored for use as a probiotic or
direct-fed microbial (DFM) in poultry feed because of its
ability to form endospores and survive the temperature and
pressure of pelleting. Each strain of B. subtilis has unique
characteristics that can determine its function and efficacy.
Therefore, information regarding a particular strain cannot
be generalized to all B. subtilis. From a practical standpoint,
the efficacy of a probiotic may be limited by factors which can
affect its application under commercial conditions.
Bacillus subtilis DSM 32315 is a strain of probiotic selected
from hundreds of naturally occurring Bacillus spp. isolates. Its
selection process was based on strict multi-parameter step
process strickt multi-parameter step process. These processes
included safety assessment, heat stability, and viability in the
chicken digestive tract. This paper will focus on two of these
multi-parameter step process: (1) Safety assessment and (2)
Although micro-organisms used as probiotics in animal feed
are generally recognized as safe, certain risks may still be associated with some probiotic strain. These include presence of
transmissible antibiotic resistance genes, presence of plasmids
or mobile genetic elements that are transferable among bacterial population present within an environment, and presence of
toxin genes e. g. enterotoxins (Shanahan, 2012; Marteau,
2001; Doron and Snydman, 2015). Therefore, it is important
to assess, at the strain level, the safety of the micro-organism
considered for use as a probiotic in animal feed.
B. subtilis DSM 32315 was assessed for toxin related genes
using B. cereus reference genes (EFSA Journal, 2014) and was
shown to contain no haemolytic enterotoxin (nheABC), hemolysin (hblCDAB), cytotoxin (cytK), or cereulide (cesA) genes.
In addition, B. subtilis DSM 32315 was evaluated for the presence or absence of plasmids, as well as antibiotic resistant
genes, based on comparison using the Comprehensive Antibiotic Resistance Database (CARD). There were no plasmid
sequences or relevant antibiotic resistance genes identified,
and this was validated by MIC assays (EFSA Journal 2012).
Based on these information, it was determined that B. subtilis
DSM 32315 is safe to be used as a probiotic in animal feed.
HEAT STABILITY IN FEED PROCESSING
Feed pelleting is a mechanical process that ensures that small
feed ingredients particles are agglomerated into larger particles by applying moisture, heat, and pressure. It has been
recognized that pelleting poultry feeds improves feed intake,
weight gain, and feed efficiency (Munt et al., 1995; Preston
et al., 2000). This may be attributed to improved feed palatability, nutrient uniformity, and alterations in ingredients such
as modification of starch and protein (Behnke, 1994; Jensen,
2000). However, the pelleting process can be detrimental to
certain feed ingredients, thereby impacting the availability of
nutrients for growth. Direct-fed microbials are a class of feed
additive which can be affected by the pelleting process. For
example, non-spore forming DFMs, such as species of Lactobacillus, Bifidobacterium, Enterococcus, and Pediococcus show a
relatively low heat stability compared to spore-forming Bacillus
sp. probiotic. It is important that a probiotic remains stable
throughout feed processing, transport, and storage, so that
when fed to the animals it can exert its activity. Therefore, two
trials were conducted to demonstrate the stability of
B. subtilis DSM 32315 spores in commercial feed processing,
and storage conditions.
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