China News Network, Kunming, September 30 (Reporter Hu Yuanhang) The Chinese Academy of Sciences Kunming Institute of Botany announced on the 30th that a research carried out by its researchers revealed the green fermentation mechanism in the traditional folk indigo dye vat, proposed eight hypotheses, including that plant ash water can be used as an alkaline medium, and rice wine can provide a source of carbon and nitrogen for microbial growth, and developed an explanation model for the traditional blue black dyeing process for the first time in combination with the hypothesis.

The relevant research results, titled Blue to black: Hypotheses on plant use complexity in traditional dynamic processes in Southeast Asia and China, were recently published in the mainstream journal Industrial Crops& On Products.
Natural indigo is one of the oldest dyes in the world. At present, traditional indigo dyeing is still carried out in various forms worldwide. Dyers use pure natural organic additives to configure dyeing vats for dyeing, but this is a complex fermentation process. Dyers from different regions, ethnic groups, and even the same region and ethnic group may use different dyeing vat formulas and various additives. In industrial indigo dyeing, converting indigo into soluble dye requires the use of a strong reducing agent, sodium hydrosulfite, which has serious impacts on the ecological environment and human health. In order to reveal the internal mechanism and principle of traditional dye vats, the research team of the Kunming Institute of Botany of the Chinese Academy of Sciences investigated and studied six "hot spots" in the global distribution of indigo plant diversity in Southeast Asia and China, including East Timor, India, Indonesia, Laos, the Philippines and Vietnam. Through bibliometric analysis and years of field investigation by the research team, we attempted to summarize the theoretical system involved in the traditional indigo dyeing process and proposed eight hypotheses for plant addition.

Research has found that the traditional indigo dyeing process is particularly clever and can effectively dissolve indigo. Dyeing indigo first and then dyeing it black: 80 plants are used in the dyeing process from blue to black, belonging to 39 families and 67 genera.
The study is based on the reasons for plant utilization obtained from field investigations, including the preparation of plant ash water, brewing, fermentation formulas, accelerated fermentation, increased color fastness, turning blue into black, and ritual plants that can bring good luck to newly formulated dyeing vats. It also includes the effective chemical or microbial substances (including reducing sugars, endophytic bacteria, quinone compounds, flavonoids, tannins, and metal ions) in plants that have been confirmed in modern research, as well as the functions of these effective substances (including plant ash water as an alkaline medium, rice wine as a source of carbon and nitrogen for microbial growth, flavonoids as electron donors, anthraquinone compounds as electron mediators, and reducing sugars as green reducing agents). Some anaerobic bacteria can directly reduce indigo, tannins can combine with indigo to form black, and metal ions can be used as mordants, The study proposes eight hypotheses regarding the use of organic additives: providing an alkaline environment, providing functional microorganisms, providing substrates for microbial growth, providing electron donors, providing electron mediators, providing reducing sugars, and providing metal or tannin mordants. Based on existing dyeing theory research and eight hypotheses, an explanatory model for the traditional blue and black dyeing process has been developed for the first time, which preliminarily explains why people add these specific plants to the dyeing vat.
The hypotheses and theories derived from this study pave the way for using natural plant products instead of chemical additives for indigo dyeing, providing a green pathway for industrial clean production. This study fills the gap between traditional knowledge and scientific principles, and emphasizes the need for further experimental work to verify the hypothesis of adding plant products to dyeing vats, hoping to provide scientific methods and theoretical basis for the application of environmentally friendly dyeing technology.