Correlation between the synthesis of pullulan and melanin in Aureobasidium pullulans

The content of pullulan and melanin in 500 mutants of Aureobasidum pullulans obtained by ultraviolet mutagenesis were examined and statistically analyzed, and a strong positive correlation was found between them. The result was further confirmed by culturing wild type strain As3.3984 in different media. Then we constructed melanin-deletion mutant As-delta alb1 and pullulan-deletion mutant As-delta pul. As-delta alb1 was a melanin-free strain with the yield of pullulan decreased by 41.01%. The supplementation of melanin in the culture of As-delta alb1 increased the production of pullulan. As-delta pul synthesized neither pullulan nor melanin and recovered melanin synthesis by adding pullulan to the medium. The results suggested that high concentration-of pullulan induced morphological transformation and synthesis of melanin, and melanin promoted the synthesis of pullulan. The pullulan biosynthetic genes, upt, pgm, ugp, and pul, were down-regulated, while the negative regulatory gene of pullulan synthesis, creA, was up-regulated by melanin deficiency. (c) 2021 Published by Elsevier B.V.

Automated summary

The study found a strong positive correlation between pullulan and melanin content; lack of melanin resulted in decreased pullulan yield, but could be increased by adding melanin; lack of pullulan could restore melanin synthesis, and high concentrations of pullulan induced morphological transformation and melanin synthesis.