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In this study, bacterial composition of iru produced by natural, uncontrolled fermentation of Parkia biglobosa seeds was assessed using culture-independent method in combination with culture-based genotypic typing techniques. PCR-denaturing gradient gel electrophoresis (DGGE) revealed similarity in DNA fragments with the two DNA extraction methods used and confirmed bacterial diversity in the 16 iru samples from different production regions. DNA sequencing of the highly variable V3 region of the 16S rRNA genes obtained from PCR-DGGE identified species related to Bacillus subtilis as consistent bacterial species in the fermented samples, while other major bands were identified as close relatives of Staphylococcus vitulinus, Morganella morganii, B. thuringiensis, S. saprophyticus, Tetragenococcus halophilus, Ureibacillus thermosphaericus, Brevibacillus parabrevis, Salinicoccus jeotgali, Brevibacterium sp. and uncultured bacteria clones. Bacillus species were cultured as potential starter cultures and clonal relationship of different isolates determined using amplified ribosomal DNA restriction analysis (ARDRA) combined with 16S–23S rRNA gene internal transcribed spacer (ITS) PCR amplification, restriction analysis (ITS-PCR-RFLP), and randomly amplified polymorphic DNA (RAPD-PCR). This further discriminated B. subtilis and its variants from food-borne pathogens such as B. cereus and suggested the need for development of controlled fermentation processes and good manufacturing practices (GMP) for iru production to achieve product consistency, safety quality, and improved shelf life.

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This study examined the growth response, nutrient utilization, biochemical and haematological properties of Clarias gariepinus juveniles, fed with graded levels of Bacillus subtilis. Five diets were formulated (35% crude protein; 3127 kCal/kg energy), comprising 0 (T1), 20 mg/100g oxytetracycline (T2), 10 5 (T3), 10 7 (T4) and 10 9 (T5) B. subtilis CFU/ml. African catfish, C. gariepinus (n=150; mean weight =94.33±0.67g) were allotted to 15 rectangular tanks and fed experimental diets apparently to satiation for 8 weeks. Growth performance, nutrient utilization, haematological and biochemical parameters were examined using standard methods. The results showed that fish fed with Diet T5 recorded significantly high values for mean weight gain (MWG) (116.67±5.70g), specific growth rate (SGR) (1.58±0.07%) and percentage weight gain (PWG) (133.62±7.47%), while Diet T1 had least values for MWG (89.00±0.58g), SGR (1.36±0.01%) and PWG (94.35±0.91g). Feed conversion ratio (FCR) and protein efficiency ratio (PER) were significantly different (p<0.05) across the test diets, with Diet T5 having the best values for FCR (1.17±0.04) and PER (3.27±0.18). No significant differences (p>0.05) were observed in the haematological, AST, ALP and GSH indices between the fish fed graded levels of probiotic and control diets. The excellent growth performance recorded at the highest inclusion level (T5) of B. subtilis showed that the probiotic could be favourably incorporated into the diet of C. gariepinus juveniles.