This study aimed to assess the variability in respect of titer and properties of xylanase from Trichoderma reesei SAF3 under both solid-state and submerged fermentation. SSF was initially optimized with different agro-residues and among them wheat bran was found to be the best substrate that favored maximum xylanase production of 219 U (gws)(-1) at 96 h of incubation. The mycelial stage of the fungi and intracellular accumulation of Ca(++) and Mg(++) induced maximum enzyme synthesis. Inoculum level of 10 × 10(6) spores 5 g(-1) of dry solid substrate and water activity of 0.6 were found to be optimum for xylanase production under SSF. Further optimization was made using a Box-Behnken design under response surface methodology. The optimal cultivation conditions predicted from canonical analysis of this model were incubation time (A) = 96-99 h, inoculum concentration (B) = 10 × 10(6) spores 5 g(-1) of dry substrate, solid substrate concentration (C) = 10-12 g flask(-1), initial moisture level (D) = 10 mL flask(-1) (equivalent to a(w) = 0.55) and the level of xylanase was 299.7 U (gws)(-1). Subsequent verification of these levels agreed (97 % similar) with model predictions. Maximum amount of xylanase was recovered with water (6:1, v/w) and under shaking condition (125 rpm). Purified xylanase from SSF showed better stability in salt and pH, was catalytically and thermodynamically more efficient over enzyme from SmF, though molecular weight of both enzymes was identical (53.8 kDa).

In the present study, the optimum conditions for the production of xylanase by immobilized spores of Trichoderma reesei SAF3 in calcium alginate beads were determined. The operational stability of the beads during xylanase production under semi-continuous fermentation was also studied. The influence of alginate concentration (1, 2, 3, and 4%) and initial cell loading (100, 200, 300, 400, and 500 beads per flask) on xylanase production was considered. The production of xylanase was found to increase significantly with increasing concentration of alginate and reached a maximum yield of 3.12+/-0.18 U ml(-1) at 2% (w/v). The immobilized cells produced xylanase consistently up to 10 cycles and reached a maximum level at the forth cycle (3.36+/-0.2 U ml(-1)).

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Clarias batrachus (Linn.) is widely recognized in Indian sub-continent for its nutritional and economic significance. At present, it remains at a merely vulnerable state. Pathogenic infections, diminution of natural habitats and introduction of allied exotic fishes are the causes of productivity constraint, particularly in Southern Asia. Conversely, African cat fish Clarias gariepinus has been significantly identified as a potential threat to biodiversity, despite being its large scale cultivation across the world. Thus emphasis on indigenous C. batrachus farming is becoming inevitable. Currently, screening of autochthonous probiotic organisms for the cultivation of C. batrachus in semi-intensive manner is getting importance. At the same time, molecular omics-based technologies are also gaining considerable attention to identify potential probiotic markers. This review provides an overall concept of probiotics, its application and future perspectives in relation to the cultivation of C. batrachus.