Protease production by Streptomyces sp. 594 was obtained after submerged fermentation (SF) and solid-state fermentation (SSF) using feather meal (FM) and corn steep liquor (CSL) as sole sources of carbon and nitrogen. Enzyme productions were 13.4 U ml(-1) in SF and 21.5 U g(-1) in SSF; these values were approximately 86% and 39% higher, respectively, than those obtained previously when yeast extract was used in place of CSL. The proteases, which belong to the serine and metalloproteinase classes, were active at high temperatures (55 degrees C to 90 degrees C) and over a wide range of pH values (5.0 to 10.0). Thus, these thermophilic proteases have shown interesting properties for industrial purposes. As far as we are concerned, this is the first contribution toward the microbial production of thermophilic proteases by a streptomycete using a low-cost medium composed of industrial poultry (FM) and corn processing by-products (CSL).

Different carbon (C) sources, mainly carbohydrates and lipids, have been screened for their capacity to support growth and lipase production by Penicillium restrictum in submerged fermentation (SmF) and in solid-state fermentation (SSF). Completely different physiological behaviors were observed after the addition of easily (oleic acid and glucose) and complex (olive oil and starch) assimilable C sources to the liquid and solid media. Maximal lipolytic activities (12.1 U/mL and 17.4 U/g) by P. restrictum were obtained with olive oil in SmF and in SSF, respectively. Biomass levels in SmF (12.2-14.1 mg/mL) and SSF (7.0-8.0 mg/g) did not varied greatly with the distinct C sources used. High lipase production (12.3 U/g) using glucose was only attained in SSF, perhaps due to the ability of this fermentation process to minimize catabolite repression.

Aims:  Protease production by Streptomyces sp. 594 in submerged (SF) and solid‐state fermentation (SSF) using feather meal, an industrial poultry residue, and partial characterization of the crude enzyme. Methods and Results:  Streptomyces sp. 594 produced proteases in SF (7·2 ± 0·2 U ml−1) and SSF (15·5 ± 0·41 U g−1), with pH increase in both media. Considering protease activity, values obtained in the liquid extract after SSF (6·3 ± 0·17 U ml−1) were lower than those from SF. The proteases, which belong to serine and metalloproteinase classes, were active over a wide range of pH (5·0–10·0) and high temperatures (55–80°C). Strain 594 was also able to degrade feather in agar and liquid media. Keratinase activity (80 U l−1) also confirmed the keratin degrading capacity of this streptomycete. Conclusions:  Proteases produced using residues from poultry industry have shown interesting properties for industrial purposes. Significance and Impact of the Study:  As far as we are concerned, this is the first contribution towards the production of thermophilic protease by a streptomycete in SSF using a keratinous waste.

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