International Journal of Waste Resources

Abstract

Newly-Isolated Laccase High Productivity Streptomyces Sp. Grown In Cedar Powder as the Sole Carbon Source

Akihisa Aoyama, Kazuhiro Yamada, Yoshinobu Suzuki, Yuta Kato, Kazuo Nagai and Ryuichiro Kurane

Microorganisms with greater potential to degrade lignin than well-known white-rot fungi were sought and identified, but the fungi were not less frequently employed for slow growth and little enzyme productivity. They were subjected to enriched cultures in order to explore the bacteria instead from 300 soil samples with cedar powder as the sole carbon source were prepared. From these, a culture with actinomycetes which showed the most oxidation activity of 2,6-Dimetoxyphenol (2,6-DMP) known as laccase substrate was selected and labeled as KS1025A strain. Characteristics of the bacteria and behavior of the secreted enzymes were examined. As a result, it was identified as a strain of Streptomyces sp. from the 16S rDNA gene sequence homology. The optimum temperature and pH for laccase activity of the secreted enzyme of this strain are 50°C and 4.5, respectively. Since Mn2+ was not directly oxidized, it was assumed that it did not contain manganese peroxidase. However, when MnSO4 was added during 2,6-DMP oxidation reaction, activity increased. After 120 hours of culture, 14 U/mL of laccase activity could be achieved by this strain, greatly exceeding known values by white rot fungus, namely 1.8U/mL after approximately 20 days. Furthermore, since reaction could continue without the addition of H2O2 during 2,6-DMP oxidation reaction, the culture solution is thought to contain free oxidizing agents. In addition, approximately 50% of 0.05% lignin sulfonic acid was decolorized by this strain in 5 days. The strain or the enzyme produced by it may be utilized for rapid biodegradation of lignin when adding hard (or soft) biomass containing lignin to produce bioethanol.