Microalgae like Spirulina (Arthrospira platensis) are protein rich and can be alternative protein sources to fishmeal and soybean meal in fish feed formulation. The present study aims to improve the protein bioavailability of Spirulina by cost-effective protein extraction followed by protease supplementation in fish feed, using in vitro studies. Different extraction procedures such as microwave-assisted, high pressure, and temperature-mediated extraction, boiling and an isoelectric precipitation were employed to study the protein yield from Spirulina powder, and this was compared with the conventional soybean meal and fishmeal conditioning during feed manufacture. Bromelain is a potent protease that has not been widely used as a feed additive with Spirulina. To study the comparative efficiency of bromelain and other proteases like papain and trypsin on Spirulina and conventional feed substrates, a protease assay was performed at different temperatures and enzyme concentrations. The digestibility of these substrates was also studied in vitro, using gut extracts from the fingerlings of Mozambique tilapia (Oreochromis mossambicus). Unlike an in vivo feeding trial, a novel method was used to study the effect of protease supplementation on the inherent digestibility of the gut with an in vitro method. Bromelain showed the highest activity on all the substrates at both the temperatures. Bromelain supplementation improved the in vitro digestibility of the Spirulina that were subjected to protein extraction, more than the un-extracted one. The results of the present in vitro study suggest that Spirulina could serve as an alternative protein source, and bromelain-based supplementation could improve the digestibility of Spirulina-based fish diets.

螺旋藻等微藻（Arthrospira platensis）富含蛋白质，可以作为鱼饲料配方中鱼粉和豆粕的替代蛋白质来源。本研究旨在通过体外研究，通过经济高效的蛋白质提取，然后在鱼饲料中添加蛋白酶来提高螺旋藻的蛋白质生物利用度。采用不同的提取程序，如微波辅助，高压和温度介导的提取，煮沸和等电沉淀，来研究螺旋藻粉的蛋白质产量，并将其与饲料制造过程中常规的豆粕和鱼粉调理相比较。菠萝蛋白酶是一种有效的蛋白酶，尚未广泛用作螺旋藻的饲料添加剂。为了研究菠萝蛋白酶和其他蛋白酶（如木瓜蛋白酶和胰蛋白酶）对螺旋藻和常规饲料底物的比较效果，在不同的温度和酶浓度下进行蛋白酶测定。还使用莫桑比克罗非鱼鱼种的肠提取物在体外研究了这些底物的消化率。Oreochromis mossambicus）。与体内喂养试验不同，采用了一种新方法来通过体外方法研究补充蛋白酶对肠道固有消化率的影响。菠萝蛋白酶在两种温度下在所有底物上均表现出最高的活性。菠萝蛋白酶补充剂改善了螺旋藻的体外消化率，而螺旋藻经蛋白质提取后的消化率要高于未提取的螺旋藻。目前的体外研究结果表明，螺旋藻可以作为蛋白质的替代来源，而基于菠萝蛋白酶的补充可以改善螺旋藻鱼饲料的消化率。