Bench scale production of nicotinic acid using a versatile amide-hydrolysing Geobacillus subterraneus RL-2a isolated from thermal spring of Manikaran, India

•Biotransformation of nicotinamide to nicotinic acid, in 1 l scale fed batch reactor.•This is the first reported Geobacillus subterraneus species having amidase activity.•This is first reported broad substrate spectrum amidase from Geobacillus sp.•Amidase with deactivation constant (kd) and enzyme t1/2 of 4.15 × 10−5 s−1 and 6 h 4 min.•The amidase showed activity at wide range of temperature (40–90 °C) and pH (4.5–13).

A new thermostable amidase-producing isolate identified as Geobacillus subterraneus RL-2a has been studied extensively for the optimization of enzyme operational conditions in the production of nicotinic acid in fed batch mode. The amidase of G. subterraneus RL-2a is constitutive in nature, active at broad pH (pH 4.5–13.0), temperature (40–90 °C) with optimal activity at 70 °C and pH 6.5. The enzyme was fairly stable at 70 °C with a deactivation constant (kd) and enzyme half-life of 4.15 × 10−5 s−1 and 6 h 4 min. Another advantage of this enzyme was its broad substrate specificity, including aliphatic, aromatic and amino acid amides respectively. In a fed batch reaction at one litre scale using resting cells corresponding to 8 U ml−1 amidase activity (7.76 mg dcw ml−1), a total of 88.6 g nicotinic acid was produced at a rate of 2.85 g h−1 g−1 dcw. This thermostable amidase represents the first reported broad substrate spectrum amidase with exceptional thermostability from a thermophilic G. subterraneus RL-2a.

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