FERMENTING RICE BRAN AS A CARBON SOURCE FOR BIOFLOC TECHNOLOGY SYSTEMS IMPROVED WATER QUALITY AND AFRICAN CATFISH Clarias gariepinus JUVENILE PRODUCTION

Nicholas Romano ^1,2*, Akeem Babatunde Dauda ¹, Ikhsan Natrah ¹, Murni Karim ¹, Mohd Salleh Kamarudin ¹

¹ Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
² Aquaculture/Fisheries Center, University of Arkansas at Pine Bluff, AR, USA 71601

Biofloc technology (BFT) is an in situ water management strategy that relies on exogenous carbon source additions, such as sugars, glycerol or starch, to increase the carbon to nitrogen (C/N) ratio that favors heterotrophic bacterial growth. These bacteria convert otherwise toxic nitrogen into potentially consumable biomass. While starches are relatively inexpensive and readily available, their low water solubility can delay the production of bioflocs, thus leading to water quality deteriorations. A potential solution could be degrading the non-starch polysachharide content. Moreover, it is known that more carnivorous speceis, such as African catfish (Clarias garipeinus) are poor collectors and consumers of bioflocs, but starches may produce larger bioflocs that may be more easily consumed that could lead to better growth.

A 42-day study was carried out to examine the effects of raw (RRB), enzymatically treated (EnRB) or fermented rice bran (FerRB), in a biofloc-based system housing C. gariepinus juveniles (9.6 g). The enzyme used in the EnRB and FerRB treatments was a proprietary product (WHITE CAP^TM; Baxel Co, Ltd., Thailand). Water quality, biofloc production/proximate composition, and subsequent effects to growth, feeding efficiencies, body proximate composition, and liver histopathology to triplicate groups were measured. A control treatment was a static system.

The FerRB had higher crude protein, water solubility and total soluble sugars as well as substaintially reduced crude fiber than RRB. Biofloc productivity were similar among biofloc treatments, but using FerRB significanlty increased biofloc crude protein and ash while causing the lowest nitrogenous waste levels. Catfish growth and whole-body crude protein was significantly higher with FerRB compared to the control, indicating some biofloc consumption.

Previous reports showed that regardless of the carbon source that included sucrose, molasses, glycerol or rice bran, BFT led to no growth improvement in C. gariepinus, likely due to this fish being inefficient biofloc collectors/consumers. This is the first study demonstrating BFT can improve catfish growth, likely due to the enhanced solubility of rice bran possibly increasing biofloc size to hence facilitate consumption. Research should continue if this protocol can similarly apply to other carnivores.