Fractionation and activity profiling of fruit bromelain from pineapples of Phuket variety growing in Thailand.

Bromelain is a type of protease found in both fruits and stems of pineapples. Stem bromelain has been extensively studied and is commercially available for applications in various industries. In contrast, studies of fruit bromelain are quite limited since most of pineapples have been consumed freshly, canned or juiced. Nowadays, the consumption of canned fruits, including canned pineapples has decreased greatly. Fruit bromelain could be a new growth point for pineapple industry. In this study, fruit bromelain was extracted from the pineapple juice of Phuket variety and some of its properties were studied. The enzyme was purified by precipitation using ammonium sulfate fractionation followed by ion-exchange and gel filtration chromatography. Consequently, the protease purification level was increased by 95.2 fold. The final specific activity was getting to 448,590 U/mg on average, dominated by cysteine proteases, with optimal activity at 45°C and pH ranging from 6 to 8. The study facilitates the molecular and application research of fruit bromelain. PRACTICAL APPLICATIONS: The research has been carried out at Funong Food Technology Co., Ltd., Guangdong, China, which produces primarily pineapple chunks and juice. As plenty of by-products, like peels and cores of pineapples, are produced, the techniques are employed to extract bromelain from the by-products. The techniques reported in this work are not new or advanced, however, they are applicable during the manufacturing process and the related equipment is easy to set up and operate. What's more, the practical application of the techniques is cost-effective for the manufactories. Take Funong Food Technology Co., Ltd. as an example, they was using 80% saturation ammonium sulfate to precipitate protein from pineapple juice and obtained a bromelain with activity of approximately 8,000 U/mg and yield of 1.7 kg per ton of juice. With the application of the techniques reported in this work, bromelain was first extracted by ammonium sulfate gradient precipitation, and then purified through ion-exchange and gel filtration chromatography. Each step of precipitation and purification generates a different level of activity and recovery of bromelain, ranging from around 2,506 to 448,590 U/mg, which allows for the production of bromelain according to the requirement of the market and brings more profits.