Published 12th February 2026

The science of tissue culture

In the latest two decades, the interest received by plant proteases has increased significantly.

Plant enzymes such as proteases are widely used in medicine and the food industry. Some proteases, like  papain, bromelain  and ficin are used in various processes such as brewing, meat softening, milk-clotting, cancer treatment, digestion and viral disorders. These enzymes can be obtained from their natural source or through in vitro cultures, in order to ensure a continuous source of plant enzymes.

Introduction

In recent decades, interest in plant natural products has grown rapidly. The number of industrially employed enzymes of plant origin is still small but growing fast. In this respect, proteases are the most commercially important enzymes due to their multiple applications in the food, pharmaceutical and detergent industries, as well as in the preparation of leather and wool, among others (Doran, 2002). Proteolytic enzymes produced commercially are used in processes such as brewing, tendernization of meat and dairy processing. The most widely utilized plant proteases are papain, bromelain and ficin, extracted from Carica papaya, Ananas comosus and Ficus carica, respectively. The present review summarizes the achievements in production of commercially relevant plant proteases both in vivo and in vitro. The focus will be on in vivo production of proteases from the four major endoprotease classes and on the tissue culture techniques that do not involve genetic modification used to improve in vitro production of these compounds.

“In a world more ancient and biologically refined than ours, plant proteases operate with remarkable precision and complexity, endowed with catalytic capabilities beyond our natural perception, performing biochemical functions we are only beginning to understand and harness.”

— Prof. George Y. P. Klu

Plant tissue culture is defined as the asceptic culture of cells, tissues, organs and their components under defined physical and chemical conditions in vitro (Thorpe, 2007). Tissues and organs can be cultured for a wide variety of purposes, among them the study of cell behavior (including cytology, nutrition, metabolism, morphogenesis, embryogenesis, and pathology), plant modification and improvement, the generation of pathogen-free plants for germplasm storage, clonal propagation, and the production of metabolites of commercial interest (reviewed in Thorpe, 2007).

Plants grown in vitro are independent of geographical and climatic factors, which is a great advantage for producing important compounds and molecules. Also, tissue culture grown plants are independent from technical and economic problems associated with cultivation in the fields, including crop diseases and heterogeneity in source material and variation in product content (Fernandez and Pomilio, 2003). Several technologies, including bioproduct formation, agricultural improvement, and plant homogenization, based on plant tissue culture techniques, have been developed (Kieran, 2001).

Plant proteases produced in vivo

As mentioned earlier, proteases have been divided into groups based on the catalytic mechanism used during the hydrolytic process (see Table 1). The main catalytic types are serine, aspartate, metallo and cysteine proteases (Bah et al., 2006). Serine and cysteine proteases are catalytically very different from aspartic and metalloproteases in that the nucleophile of the catalytic site is part of an amino acid, whereas it is an activated water molecule in the other two groups (Bruno et al., 2006)

Other resources

• K.I. Abraham et al. Studies on proteinases from Calotropis gigantea latex. I. Purification and some properties of two proteinases containing carbohydrateBiophys Acta(1979)
• B. Andallu et al. Effect of mulberry (Morus indica) therapy on plasma erythrocyte membrane lipids in patients with type 2 diabetes Clin Chim Acta (2001)
• B. Andallu et al. Antioxidant role of mulberry (Morus indica L. cv. Anantha) leaves in streptozotocin-diabetic rats Clin Chim Acta (2003)

Since proteases are often expensive, especially at high degrees of purity, development of strategies that will produce structural and functional homogeneous compounds, such as callus and cell suspension cultures, may increase their industrial applicability. In spite of the availability of proteolytic enzymes from genetically engineered microorganisms or animals, the search for sources of plant origin for use in the food industry is increasing in order to satisfy the social demands for such products. In many cases it would not be possible to allocate land for the cultivation of species with the sole purpose of producing enzymes. However, one of the many advantages of tissue culture techniques such as cell suspension cultures grown in bioreactors would be the possibility of obtaining a high total activity of protease due to the high amount of biomass in the medium. Furthermore, the cultivation of plant cells in bioreactors overcomes the problems that might arise from climatic, seasonal, environmental and political changes.