α-L- rhamnosidases Produced under Solid State Fermentation by Few Aspergillus Strains

The production of α-L-rhamnosidase from Aspergillus ochraceous MTCC -1810, A. wentii MTCC- 1901, A. sydowii MTCC- 635, A. foetidus MTCC-508 under solid- state fermentation using easily available agro- industrial residues such as corn cob, rice bran, sugarcane bagasse, wheat bran and citrus peel as substrate. Among these, sugarcane bagasse in combination with naringin and sucrose were found to be the best substrate. The α-L-rhamnosidase production was highest after the 4th day of incubation at 30ºC and a substrate to moisture ratio of 1:1 w/v. Supplementation of the medium with 10% naringin caused the maximum production of the enzyme. The temperature optima and pH optima of α-L-rhamnosidases were determined in the range of 50-60ºC and 4.0-5.0 respectively. The α-L-rhamnosidases secreted from the above fungal strains is suitable for the debittering of orange fruit juice.

Purification and characterization of Mn-peroxidase from Musa paradisiaca (banana) stem juice.

Mn-peroxidase (MnP), a biotechnologically important enzyme was purified for the first time from a plant source Musa paradisiaca (banana) stem, which is an agro-waste easily available after harvest of banana fruits. MnP was earlier purified only from the fungal sources. The enzyme was purified from stem juice by ultrafiltration and anion-exchange column chromatography on diethylamino ethylcellulose with 8-fold purification and purification yield of 65%. The enzyme gave a single protein band in SDS-PAGE corresponding to molecular mass 43 kDa. The Native-PAGE of the enzyme also gave a single protein band, confirming the purity of the enzyme. The UV/VIS spectrum of the purified enzyme differed from the other heme peroxidases, as the Soret band was shifted towards lower wavelength and the enzyme had an intense absorption band around 250 nm. The Km values using MnSO4 and H2O2 as the substrates of the purified enzyme were 21.0 and 9.5 μM, respectively. The calculated kcat value of the purified enzyme using Mn(II) as the substrate in 50 mM lactate buffer (pH 4.5) at 25°C was 6.7s-1, giving a kcat/Km value of 0.32 μM-1s-1. The kcat value for the MnP-catalyzed reaction was found to be dependent of the Mn(III) chelator molecules malonate, lactate and oxalate, indicating that the enzyme oxidized chelated Mn(II) to Mn(III). The pH and temperature optima of the enzyme were 4.5 and 25°C, respectively. The enzyme in combination with H2O2 liberated bromine and iodine in presence of KBr and KI respectively. All these enzymatic characteristics were similar to those of fungal MnP. The enzyme has the potential as a green brominating and iodinating agent in combination with KBr/KI and H2O2.

Enzymatic characteristics of quercetinases from some indigenous Aspergillus flavus strains.

Five indigenous Aspergillus flavus strains MTCC-2206, 1884, 1883, 1783 and 2456 were screened for the secretion of quercetinase. Fungal strains MTCC-2206, 1884, 1883, and 1783 were found to secrete the quercetinase in the range of 0.24-0.36 enzyme unit/mL of the culture medium, while MTCC-2456 secreted only 0.04 enzyme unit/mL. The enzymatic characteristics of quercetinase were determined. The Km values using quercetin as the substrate were 12.5 microM, 14.0 microM, 12.5 microM and 13.0 microM for the quercetinase produced by MTCC-2206, 1884, 1883 and 1783, respectively. The pH optima for the above enzymes were 6.5, 6.5, 6.0 and 6.0 and temperature optima were 45, 40, 45 and 50 degrees C, respectively. The partial purification from only one strain MTCC-2206 was achieved (nearly 3-fold purification).

Purification of a peroxidase from Solanum melongena fruit juice.

Solanum melongena fruit juice contains peroxidase activity of the order of 0.125 IU/mL. A method for the 11-fold purification of the enzyme was developed. The Km values of the peroxidase for the substrates guaiacol and hydrogen peroxide were 6.5 mM and 0.33 mM, respectively. The pH and temperature optima were 5.5 and 84 degrees C, respectively using guaiacol as the substrate. Sodium azide and phenyl hydrazine inhibited the enzyme competitively.

Enzymatic characteristics of ligninperoxidases from Penicillium citrinum, Fusarium oxysporum and Aspergillus terreus using n-propanol as substrate.

The activities of ligninperoxidases from Penicillium citrinum MTCC 3565, Fusarium oxysporum MTCC 3379 and Aspergillus terreus MTCC 3374 have been assayed and the enzymatic characteristics like Km, pH and temperature optima using n-propanol as the substrate have been reported. The results suggest that n-propanol can substitute veratryl alcohol as substrate for assaying ligninperoxidase activities from different fungal strains, without affecting the enzymatic characteristics. The above strains were selected, as they were known to secrete ligninperoxidase in the liquid culture medium.

Secretion of ligninperoxidase by Penicillium citrinum, Fusarium oxysporum and Aspergillus terreus.

Secretion of ligninperoxidase [E.C.1.11.1.7] by Penicillium citrinum, Fusarium oxysporum and Aspergillus terreus in liquid culture growth medium has been demonstrated. Enzymatic characteristics like Km, pH and temperature optima using veratryl alcohol as the organic substrate of ligninperoxidases from above sources have been determined. Km values using veratryl alcohol as substrate for enzymes from P. citrinum, F. oxysporum and A. terreus were 69, 64 and 60 microM respectively. Km values using H2O2 as the variable substrate were 64, 72 and 80 microM.The pH optima were 4.0, 2.3 and 2.0 respectively. The values of temperature optima were 30 degrees, 25 degrees and 22 degrees C for the enzymes from P. citrinum, F. oxysporum and A. terreus respectively.