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In a new approach to microbial gallic acid production by Aspergillus fischeri MTCC 150, 40gL -1 of tannic acid was added in two installments during the bioconversion phase of the process (25gL -1 and 15gL -1 at 32 and 44h respectively). The optimum parameters for the bioconversion phase were found to be temperature: 35ºC, pH: slightly acidic (3.3-3.5), aeration: nil and agitation: 250 rpm. A maximum of 71.4% conversion was obtained after 71h fermentation with 83.3% product recovery. The yield was 7.35 g of gallic acid per g of biomass accumulated and the fermenter productivity was 0.56 g of gallic acid produced per liter of medium per hour.

SummaryHaloarchaea are found at very high concentrations in salt-conditioned environments, hence produce enzymes which are able to catalyze reactions under harsh conditions, typical of many industrial processes. In the present study, culture conditions for extracellular amylase production from Haloarchaea isolated from a solar saltern were optimized and the purifi ed enzyme was characterized. Haloferax sp. HA10 showed maximum amylase production at 3 M NaCl, 37 °C, pH=7 and 1 % starch content. Purifi ed α-amylase was a calcium-dependent enzyme with an estimated molecular mass of about 66 kDa and many industrially useful properties. It was found to be stable in a broad range of pH (from 5 to 9) and NaCl concentrations (from 0.5 to 3.0 M), retaining 48 % activity even at 4 M. The optimal temperature for Haloferax sp. HA10 amylase activity was 55 °C (99 % activity), and 57 % activity was retained at 80 °C, which dropped to 44 % with the increase of temperature to 90 or 100 °C. It was able to sustain various surfactants and detergents. To the best of our knowledge the detergent-stable α-amylases from halophilic archaeon have not been reported yet.

A spectrophotometric method to determine gallic acid, residual gallotannin and tannin acyl hydrolase (EC 3.1.1.20) activity during microbial hydrolysis of pentagalloyl glucose is described. The following equations have been developed to estimate gallotannin and gallic acid in the incubation medium by absorbance measurements at two different wavelengths: concentration of gallotannin (μg ml(-1))=34.41 (A293.8)-6.98 (A254.6); concentration of gallic acid (μg ml(-1))=21.77 (A254.6)-17.17 (A293.8). As compared to Aspergillus and Penicillium, the fungal genera extensively studied for the production of this enzyme, Fusarium solanii and Trichoderma viride exhibited higher enzyme activity showing approximately 88 and 84 mole percent conversion respectively after a 24 h incubation period.

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