ORIGINAL ARTICLE Evaluation of growth, feed utilization efficiency and immune parameters in tiger shrimp (Penaeus monodon) fed diets supplemented with or diet fermented with gut bacterium Bacillus sp. DDKRC1. isolated from gut of Asian seabass (Lates calcarifer) Debasis De 1 | Ramalingam Ananda Raja 2 | Tapas Kumar Ghoshal 1 | Suchita Mukherjee 1 | Koyadan Kizhakedath Vijayan 2 1 Kakdwip Research Centre of ICAR-Central Institute of Brackishwater Aquaculture, Kakdwip, West Bengal, India 2 ICAR-Central Institute of Brackishwater Aquaculture, Chennai, Tamil Nadu, India Correspondence Debasis De, ICAR-Central Institute of Brackishwater Aquaculture, Chennai, Tamil Nadu, India. Emails: debasiskrc@yahoo.com; dedebasis47@gmail.com Funding information Department of Biotechnology, Ministry of Science & Technology, Government of India Summary An experiment was conducted to assess the effect of supplementation of cellulolytic gut bacterium with plant protein-based diet on growth, digestibility and digestive enzyme status of tiger shrimp, Penaeus monodon. Bacillus sp. DDKRC1. (JN641289), a potential cellulolytic bacterium, isolated from the gut of Asian seabass was used as feed supplement in this experiment. The shrimps of group I, II and III were fed with control diet (without bacterial supplement, D1), diet supplemented with live Bacillus sp. DDKRC1. at 2.94 9 10 7 cfu per 100 g feed (D2) and diet fermented (48 hr) with same bacteria (D3) respectively. At the end of the 42 days experiment, shrimps of group II showed significantly better (p < .01) growth and protein effi- ciency ratio (PER) and lower (p < .01) feed conversion ratio (FCR) as compared to group I and III. Dry matter, cellulose, hemicellulose and lipid digestibilities were sig- nificantly (p < .01) higher in group II than other two groups. Cellulase, amylase and protease activities in the gastrointestinal (GI) tract were significantly (p < .01) higher in group II as compared to other two groups. Total heterotrophic count, amylolytic, cellulolytic and proteolytic bacterial counts in gut were significantly (p < .01) higher in group II as compared to other two groups. Haematological analysis indicated bet- ter (p < .05) immune response in groups II and III than control group. Diets D2 and D3 showed better effect on growth, digestibility, FCR, survival and immune response of P. monodon as compared to D1. KEYWORDS Bacillus sp. DDKRC1., digestibility, growth, gut bacteria, immune parameters, Penaeus monodon 1 | INTRODUCTION The use of live bacterial supplementation (probiotics) in aquaculture is increasing day by day for more ecofriendly aquaculture practices (Gatesoupe, 1999). Probiotic agents exert a beneficial effect through enzymatic assistance to digestion and absorption of nutrients in gastrointestinal tract of host (Erasmus, Cook & Coyne, 1997; Krish- naprakash, Saravanan, Murugesan & Rajagopal, 2009; Sahu, Swar- nakumar, Sivakumar, Thangaradjou & Kannan, 2008), competition for adhesion sites and resistance to colonization (Balc azar et al., 2006; Verschuere, Rombaut, Sorgeloos & Verstraete, 2000), competition for essential nutrients, reduction in gut pH, production of DOI: 10.1111/are.13669 Aquaculture Research. 2018;1–9. wileyonlinelibrary.com/journal/are © 2018 John Wiley & Sons Ltd | 1