**4.3 Acidifiers**

A plethora of studies confirmed that high amounts of dietary FM could be substituted with APPS by supplementing diet with short-chain fatty acids and acidifiers [80, 81]. In fact, acidification of plant protein based aquafeeds with acidifiers increase the bioavailability of minerals and trace elements and they neutralize or alleviate the negative impacts of ANF on nutrients digestibility [60, 82–84]. In addition, acidifiers by reducing the chyme pH through the gut can induce the pepsin activity [85]. Moreover, reduction of the chyme pH triggers the release of gastrointestinal hormones (*e.g.* secretin and cholecystokinin) that stimulate secretion of pancreatic digestive enzymes, which in turn elevates the digestibility of protein and minerals. Furthermore, it has been reported that acidifiers by controlling the appetite through the parasympathetic nerve system including orexigenic neurotransmitters that increase feed efficiency [86].

#### **4.4 Gut microbiota as ANF biodegrading agent in fish**

The application of the gut "indigenous" microbiota as probiotics can improve feed digestibility by supplying exogenous enzymes (*e.g.* cellulase, phytase, tannase and xylanases) and by eradicating and/or reducing ANF of the plant protein


*Legumes, Sustainable Alternative Protein Sources for Aquafeeds DOI: http://dx.doi.org/10.5772/intechopen.99778*

**Table 3.**

*Legume bioactive compounds neutralizing strategies.* ingredients in the fish gut [87]. A plethora of studies have recognized cellulaseproducing bacteria such as *Citrobacter sp. C. freundii, Enterobacter* sp. *Bacillus coagulans*, *B. cereus*, *B. subtilis* P6, *B. velesensis* P11, *B. pumilus*, *B. tequilensis* (KF640219), *B. megaterium* (KF640220) and *B. altitudinis* from the gut of various cultured fish species including Chinese carps [88, 89], Indian major carps [90, 91], tilapia (*Oreochromis mossambica*) [92], bata fish [93], murrels (*Channa punctatus*) [94], pacu (*Piaractus mesopotamicus*) and piaucom-pinta (*Leporinus friderici*) [95]. Using the above mentioned microorganisms as potential probiotics in aquafeeds or applying these microorganisms for fermentation of plant protein ingredients can provide great potential for eradicating ANF and improving their nutritional quality by boosting up EAA, minerals and vitamins bioavailability and increasing digestibility of protein and energy.
