For environmental benefits and sustainability, the development of green technology has gradually gained attention. Ultrasound is a nonthermal technology that can be used in various fields as a green technology. Ultrasound can produce cavities in the liquid phase, which can promote chemical reactions through the violent collapse of bubbles and generation of hotspots. The growth and collapse of bubbles under ultrasound is known as cavitation. Such a phenomenon can be used for releasing enzymes, promoting enzymatic hydrolysis, improving extraction efficiency, and increasing mass transfer in bioconversion and the processing of food and agricultural byproduct.

The major direction for Dr. Yang’s research is to use ultrasound and microorganisms in food and agricultural byproduct, and this research is divided into two parts: (1) microorganisms and ultrasound in food fermentation and biotransformation and (2) the use of ultrasound in bioconversion and agricultural byproduct processing. In addition, kinetics were explored to understand the mechanisms of reaction.

The investigation of microorganisms and ultrasound in the food fermentation and biotransformation

Probiotics play a crucial role in food fermentation, and lactic acid bacteria (LAB) are widely used as probiotics and starter cultures in the fermentation of dairy products, vegetables, and meat. Recently, LAB as probiotics have been reported to exhibit health benefits, such as the inhibition of intestinal pathogens, reduction of blood cholesterol, modulation of the immune system, and prevention of cancer. Moreover, some intracellular enzymes of LAB and other probiotics can promote the functions of fermented food. Thus, the development of ultrasonic irradiation to enhance the release and activity of enzymes is crucial in food fermentation and biotransformation of active compounds to substantially improve the functionality and nutrients of fermented products to benefit human health.

The application of ultrasound in the bioconversion and processing of agricultural byproduct

Agricultural byproduct (leaf, straw, and husk) is the valuable biomass obtained from agricultural harvesting and processing, and it contains lignocellulosic polymers, which are the most promising source of renewable energy; thus, such biomass can serve as raw material for biofuel production. However, such materials are surrounded by cuticle silica or wax, which impedes enzyme and microorganism hydrolysis and conversion. This difficulty may be overcome through an effective process including pretreatment and hydrolysis of biomass. Therefore, ultrasound is worthy of investigation for application in the bioconversion of biomass.