A fungal strain (Conidiobolus brefeldianus MTCC 5184) isolated from plant detritus secreted a high activity alkaline protease. Thermostability studies of the fungal alkaline protease (FAP) revealed that the protease is stable up to 50°C with 40% residual activity after one hour. Effect of various additives such as sugars, sugar alcohols, polyols, and salts, on the thermostability of FAP was evaluated. Among the additives tested, glycerol, mannitol, xylitol, sorbitol, and trehalose were found to be very effective in increasing the stability of FAP, which was found to be concentration dependent. Fivefold increase in residual activity of FAP was observed in the presence of trehalose (50%) and sorbitol (50%) at 50°C for 4 h, compared to FAP without additive. Other additives like calcium at 20 mM and 10–15% ammonium sulphate showed lower stability improvement than trehalose and sorbitol. NaCl, MgCl2, K2HPO4, and glycine were found to be poor stabilizers and showed only a marginal improvement. PEG 6000 did not show any increase in stability but was found to be slightly inhibitory.
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机译：从植物碎屑中分离出的真菌菌株（Conidiobolus brefeldianus MTCC 5184）分泌了高活性碱性蛋白酶。真菌碱性蛋白酶（FAP）的热稳定性研究表明，该蛋白酶在高达50°C的温度下稳定一小时后具有40％的残留活性。评估了各种添加剂（如糖，糖醇，多元醇和盐）对FAP的热稳定性的影响。在所测试的添加剂中，发现甘油，甘露醇，木糖醇，山梨糖醇和海藻糖对提高FAP的稳定性非常有效，而FAP的稳定性与浓度有关。与没有添加添加剂的FAP相比，在海藻糖（50％）和山梨糖醇（50％）在50°C下存在4 for h时，FAP的残留活性增加了五倍。其他添加剂，例如20 mM的钙和10-15％的硫酸铵，显示出比海藻糖和山梨糖醇更低的稳定性。发现NaCl，MgCl2，K2HPO4和甘氨酸是较差的稳定剂，仅显示出少量的改善。 PEG 6000没有显示出任何稳定性的增加，但是被发现具有轻微的抑制性。
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