Probiotic Applications in Crustaceans - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 296

11.2.2 Lactic acid bacteria (LAB)
Another approach to the development of new probiotic applications in crustacean aquaculture
consists in testing proven human or terrestrial animal probiotics such as strains of lactic acid
bacterial (LAB) species. Because LAB are the most commonly applied probiotics in terres-
trial animal nutrition, their use as probiotics has been proposed for aquatic species (Ringø
and Gatesoupe 1998). Moreover since regulations in many countries make it mandatory to get
authorization for the use of probiotics in animal feeds, the use of already identified and docu-
mented bacterial species, such as LAB or those belonging to the genus Bacillus , will tend to
be increasingly extended to aquaculture (Gatesoupe 2002) as the licensing of new species is
relatively expensive (Hong et al. 2005).
LAB potentially have several interesting probiotic properties: they are generally recognized
as safe (Leuschner et al. 2010), they have the ability to adhere to cells, they may stimulate the
growth of beneficial microorganisms and outcompete harmful bacteria, and they reinforce the
organism's natural defence mechanisms (Reid 1999; Vázquez et al. 2005). For instance, as
reviewed in the previous chapters a large number of probiotic studies report the beneficial
effects of LAB probiotics on immunological and haematological parameters in fish, although
the immunomodulatory mechanisms are only partly described.
Contrary to what is recorded in fish, in crustaceans most of the studies on intestinal micro-
biota do not report the presence of LAB in their digestive tract (for a review see Chapter 6 ).
However, the current knowledge on the intestinal microbiota of crustaceans is still very limited
and the majority of studies conducted so far have used conventional culture based microbiolog-
ical methods, therefore providing incomplete information (Dempsey et al. 1989; Harris 1993;
Moss et al. 2000; Oxley et al. 2002). Only a limited number of studies have used molecular
methods to describe the microbiota of shrimps (Li P. et al. 2007; Johnson et al. 2008; Castex
2009; Liu et al. 2011a) or other crustaceans (Battison et al. 2008; Daniels et al. 2010). Further
work in this direction is essential to better understand the presence, diversity and role of the
intestinal microbial populations in crustaceans, and manipulate them in a way which promotes
a better host health status. Even if the presence of LAB as normal inhabitants of the digestive
tract of crustacea still needs to be addressed, the continual application of LAB species to crus-
taceans may lead to high GI levels of LAB and modulated microbial populations. Castex et al.
(2008) reported that Ped. acidilactici MA18/5M administered continuously at a concentration
close to 10 7 CFU g -1 of feed was retrieved at levels between 10 4 and 10 5 CFU g -1 in the gut
of Litopenaeus stylirostris . This result was associated with a significant decrease in the Vib-
rio spp. levels in the intestine. Similar observations, Vibrio inhibition and probiotic recovery
were reported in the intestine of L. vannamei fed a diet supplemented with an autochthonous
Lactobacillus plantarum at 2 × 10 7 CFU -1 (Viera et al. 2008). Unfortunately, studies with
LAB probiotics have rarely reported the probiotic count achieved in the digestive tract of the
host, but interestingly levels of recovered probiotic similar to those reported in these two stud-
ies on penaeid shrimps were also reported with Bacillus spp. probiotics on P. monodon and
Fenneropenaeus indicus (Rengpipat et al. 2000; Ziaei-Nejad et al. 2006), suggesting an opti-
mal probiotic bacteria level between log 4 and 6 CFU g -1 in the intestine of penaeid shrimps.
As with fish, the effect of LAB on the immunological response of crustaceans has also been
addressed, especially in penaeid shrimps. For instance, Chiu etal. (2007) investigated the effect
of an Lb. plantarum strain on several immune parameters of L. vannamei . The author's report
that administering this strain of Lb. plantarum can enhance the non-specific immunity (phe-
noloxidase (PO) activity, as well as prophenoloxidase (proPO) and peroxinectin (PE) mRNA