Biodegradable Film from Kombucha SCOBY Culture using Different Types of Tea Extracts with or without Glycerol

Abstract

The use of single-use plastic goods causes serious pollution in many countries, contributing significantly to environmental waste. This environmental crisis creates a necessity for developing sustainable, biodegradable packaging materials. Furthermore, in the rapidly growing kombucha industry, the symbiotic culture of bacteria as well as yeast produces an additional cellulose layer that is usually discarded, which adds to the waste generation. While previous research has established the use of symbiotic culture of bacteria and yeast (SCOBY) as a biopolymer and demonstrated that plasticizers can improve film flexibility, there was a lack of comparative data on how different tea types impacted the physical, thermal, and mechanical properties and antioxidant activity of SCOBY films after modification with glycerol. Hence, this study aimed to fabricate biodegradable SCOBY films using three different tea extracts ((black (BT), green (GT), and combination (BTGT)) with/without glycerol coating, determine the physical properties (thickness, color, water solubility, degradation rate, and thermal properties) and mechanical properties, and antioxidant capacity (DPPH activity) of the developed SCOBY films. GT produced the thickest SCOBY films (0.9 mm), significantly lighter (L = 71.34) and exhibited a greener hue, while BT films were darker (L = 46.50). SCOBY films coated with glycerol increased both water solubility (from ~6.6% to ~54%) and biodegradability rate (e.g., GT from 19.81% to 33.50%). This effect is linked to glycerol’s hydrophilic nature and its role in forming hydrogen bonds, which enhances water absorption and promotes breakdown. There was a greater degradation rate (19.81%) of GT films than BT (16.00%), which was possibly attributed to the preservative property of tannins in black tea. Uncoated BT films had the highest tensile strength (0.27 MPa) and the elongation at break (34.48%), but tannins were used as natural reinforcing agents. Glycerol coating was a plasticizer, which had a major reduction in tensile strength (e.g., BT decreased from 0.27 MPa to 0.17 MPa) and at the same time an increase in flexibility (elongation). The DPPH antioxidant activity (38.03% uncoated and 59% with glycerol) was also highest in GT films. The activity of DPPH was supported by glycerol, which stabilized and solubilized these antioxidants. To sum up, tea type is the main determinant of color and antioxidant activity, whereas glycerol is the most effective plasticizer and has a considerable influence on solubility, flexibility, and thermal stability.