Probiotic Applications in Crustaceans - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 295

to 10 10 CFU g -1 of diet, could (1) increase growth and survival in pond and tank culture,
(2) increase resistance to pathogenic V. harveyi strains, (3) activate both cellular and humoral
immune defences, and (4) provide competitive exclusion in the shrimp gut. Meunpol et al.
(2003) confirmed the efficiency of this strain and reported, in association with an ozone treat-
ment, the beneficial effect conferred by Bacillus S11 on the survival of P.monodon post larvae,
concomitantly with a reduction in V. harveyi concentration in the culture water. More recently,
evaluations of Bacillus spp. probiotics were conducted on other crustacean species. Daniels
et al. (2010) investigated the effect of a combination of dietary Bacillus sp. and yeast man-
nan oligosaccharides (MOS) on European lobster ( Homarus gammarus L.) larvae. Beyond the
classic effects on performance and survival, this study highlights for the first time the effect of
a Bacillus spp. mixture on various parameters of lobster larvae such as modification in the gut
microbial communities and improvements in intestinal morphology.
As described later in this chapter, one of the mechanisms of action by which Bacillus spp.,
especially B. subtilis , provide host benefits is by modulation of the immune response of the
host. Such effects have been well documented in humans, terrestrial animals (Green et al.
1999; Cutting et al. 2011), fish (Avella et al. 2010) and also in crustaceans (Tseng et al. 2009;
Liu et al. 2011b). The effect of Bacillus spp. on digestion and their putative contribution to
nutritional processes have also been evaluated in crustaceans.
It is important to add here that Bacillus strains are also being studied, and extensively used,
as bioremediation agents in shrimp farming (Moriarty 1999). The potential role and benefits
of such microorganisms on the nutrient cycle and microbial processes in aquaculture ponds
have been described by Moriarty (1997) and readers with a specific interest in this topic are
referred to that review article. For instance, the author compared results from different farms in
the Philippines and concluded that the addition of several Bacillus spp. to the pond water, at a
concentration of 10 4 to 10 5 CFU ml -1 , allowed the culturing of shrimps over 160 days without
an outbreak of luminescent Vibrio disease, while control ponds were affected by luminescent
Vibrio disease before 80 days of culture (Moriarty 1998; 1999). The author demonstrated that
the probiotic treatment modified the bacterial species composition of the pond water and sedi-
ment with a particular reduction in the number of luminous Vibrio spp. Apart from pathogenic
bacteria, another main concern in intensive shrimp farming is organic enrichment and nitroge-
nous waste, including ammonium and ammonia in the culture pond. In relation to this, probi-
otics such as selected Bacillus spp. (Moriarty 1998; Song et al. 2011), eventually coupled with
other bacterial strains (Devaraja etal. 2002; Matias etal. 2002; Wang and He 2011), have been
added to pond water with the aim of boosting mineralization of the organic matter and increas-
ing water quality. Thus, bacterial species belonging to the Bacillus , Pseudomonas , Acinetobac-
ter , Cellulomonas , Rhodopseudomonas , Aerobacter , Nitrosomonas and Nitrobacter genera are
known to promote mineralization of organic wastes (Thomas et al. 1992). For instance, Nitro-
somonas spp. will help in the oxidation of ammonia while Nitrobacter spp. will oxidize nitrites
and this process can help to prevent the build-up of toxic ammonia. Recently, a B. coagu-
lans strain isolated from highly intensive shrimp ponds in China was also reported to show
interesting aerobic denitrification characteristics for nitrite removal in shrimp ponds (Song
et al. 2011). Some of the benefits of using such bacterial products include the reduction of
blue-green algal populations and of nitrate, nitrite, ammonia and phosphate levels, the increase
of dissolved oxygen concentrations and the promotion of organic matter decomposition (Boyd
1995). Unfortunately well designed studies on the benefits of applying such bacterial products
in aquaculture rearing systems are still scarce (Shariff et al. 2001; Devaraja et al. 2002).