Indigofera Tinctoria Leaf Powder As A Promising Additive To Improve Indigo Fermentation Prepared With Sukumo (Composted Polygonum Tinctorium Leaves)

Abstract

Being insoluble in the oxidize form, indigo dye must be solubilized by reduction for it to penetrate textile. One of the procedures is the reduction by natural bacterial fermentation. Sukumo, composted leaves of Polygonum tinctorium, is a natural source of indigo in Japan. Although sukumo has an intrinsic bacterial seed, the onset of indigo reduction with this material may vary greatly. Certain additives improve indigo fermentation. Here, we studied the effects of Indigofera tinctoria leaf powder (LP) on the initiation of indigo reduction, bacterial community, redox potential (ORP), and dyeing intensity in the initial stages and in aged fermentation fluids prepared with sukumo. I. tinctoria LP markedly decreased ORP at day 1 and stabilised it during early fermentation. These effects could be explained by the phytochemicals present in I. tinctoria LP that act as oxygen scavengers and electron mediators. Using next generation sequencing results, we observed differences in the bacterial community in sukumo fermentation treated with I. tinctoria LP, which was not influenced by the bacterial community in I. tinctoria LP per se. The concomitant decrease in Bacillaceae and increase in Proteinivoraceae at the onset of fermentation and the ratio of facultative to obligate anaerobes are vital to the for initiation and maintenance of indigo reduction. Hence, I. tinctoria LP improved early indigo reduction by decreasing the ORP and hasten the appropriate transitions in the bacterial community in sukumo fermentation.

Indigofera tinctoria L. leaf powder promotes initiation of indigo reduction by inducing of rapid transition of the microbial community

“…LP acts to accelerate indigo reduction in the natural fermentation of D- sukumo , which produces slow change in microbiota during fermentation ( Lopes et al, 2021a ). In this study, we aim to confirm the accelerative effect of LP on microbiota using T- sukumo , which without LP would produce rapid change in microbiota, and D- sukumo , which without LP would produce slow change in microbiota.…”

“…A previous study reported that a stable state under alkaline anaerobic conditions, that induced dominance of the obligate anaerobe Proteinivoraceae was an important factor for maintaining of indigo fermentation for long period ( Tu et al, 2019b ). However, even in anaerobic conditions dominated by family Proteinivoraceae , which is equivalent to genus Alkalicella , at the beginning of the fermentation, indigo reduction was not initiated ( Lopes et al, 2021a ). In the present study, we confirm the more specific prerequisite phase transition of microbiota that is required for indigo reduction.…”

“…Indigo reduction was initiated later than day 10 from fermentation fluid prepared using this sukumo . In a previous report, it took 58 days for obvious dyeing to appear ( Lopes et al, 2021a ). The sukumo mixed with wood ash extract as described above produced four different batches.…”

“…The effects of LP on slow-changing microbiota indigo fermentation employed sukumo produced in Date, Hokkaido, Japan (D- sukumo ) have already been studied ( Lopes et al, 2021a ). However, the pH of the fermentation fluid fluctuated between pH 10.5 and pH 11.8.…”

“…Although it is difficult to regulate microbiota to a desirable state, the microbiota in indigo fermentation can be regulated in a manner suitable for indigo reduction, acceleration of initiation of indigo reduction will be possible ( Lopes et al, 2021a ). We found that addition of Indigofera tinctoria L. leaf powder (LP) to the fluid at the beginning of its fermentation reduced redox potential and promoted the appropriate transition in the microbiota of the fluid.…”