Enzymatic Hydrolysis Intensification of Lignocellulolytic Enzymes Through Ultrasonic Treatment

Ultrasound technology is often associated with harmful effects on enzyme reactions, although it is possible to improve the productivity of bioprocesses when suitable conditions are employed. Sugarcane bagasse and straw are the feedstocks widely used in Brazil for second-generation (2G) ethanol production; however, the lignocellulose biomass conversion into fermentable sugars through the enzymatic route is not yet fully optimized. Lignocellulolytic enzymes represent a significant part of the costs related to 2G ethanol production. Nonetheless, they exhibit great potential for cost reduction due to improved enzyme features: mainly increment of its activity and an increase of hydrolysis yield. This enzymatic hydrolysis of feedstock can be enhanced by green technology ultrasound application’s combined action on the enzymes and their substrates. The mixed action increases the lignocellulose saccharification; hence, it is considered a promising alternative for fermentable sugar release. The process optimization using green approaches, such as ultrasound and enzymatic treatment, can boost the sugar yield, thus emphasizing the importance of steps integration towards biomass conversion. This review attempts to provide an overview of the effects of ultrasound treatment on lignocellulolytic enzymes used in the 2G ethanol production and those of the process intensification through an unprecedented bibliometric search.