No abstract

Microalgae are known to be a potential resource of high-value metabolites that can be used in the growing field of biotechnology. These metabolites constitute valuable compounds with a wide range of applications that strongly enhance a bio-based economy. Among these metabolites, astaxanthin is considered the most important secondary metabolite, having superior antioxidant properties. For commercial feasibility, microalgae with enhanced astaxanthin production need to be developed. In this study, the tropical green microalgae strain, Coelastrum sp., isolated from the environment in Malaysia, was incubated with methyl viologen, a reactive oxygen species (ROS) reagent that generates superoxide anion radicals (O2-) as an enhancer to improve the accumulation of astaxanthin. The effect of different concentrations of methyl viologen on astaxanthin accumulation was investigated. The results suggested that the supplementation of methyl viologen at low concentration (0.001 mM) was successfully used as a ROS reagent in facilitating and thereby increasing the production of astaxanthin in Coelastrum sp. at a rate 1.3 times higher than in the control.

Highlights A newly isolated Coelastrum sp. improved the yield of astaxanthin by chemical mutagenesis. Mutagenesis using chemical mutagen of EMS attempted to increase the microalgae biomass and carotenoid production in Coelastrum sp. High-throughput screening method using glufosinate successfully expedited astaxanthin production in a mutated strain of a Coelastrum sp. The selected mutant using glufosinate exhibited an increase of astaxanthin content with ∼2-fold higher compared to the wild type.

Alien, introduced, and non-native species expand their distribution through the development of various transportation networks. In Japan, Ligustrum lucidum Aiton (Oleaceae) was introduced in the mid-1800s for use as roadside trees, but has escaped from the planting area and spread everywhere. This species also invades coastal areas and has adapted to develop its characteristic features under various stress conditions. To clarify the adaptive features of L. lucidum in coastal areas, we conducted morphological and anatomical analyses. We found that the stomatal size of L. lucidum was smaller in the coastal populations than in inland populations, which is similar to the coastal adaptation pattern of L. japonicum Thunb., a closely related native species. Our results suggest that strong selective pressure on coastal area conditions could force their leaves to avoid excessive transpiration, and such an adaptation pattern of L. lucidum could expand its distribution to various coastal areas.

We examined the species composition, stand structure and distribution pattern of coastal forest which composed by broad-leaved tree species in Horikiri coast Atsumi peninsula, Aichi prefecture. The sites were classified into the four groups by TWINSPAN. And the groups changed from seaside to landside. For the distribution pattern of broad-leaved tree species, Euonymus japonicas, Pittosporum tobira and Ligustrum ovalifolium concentrated on seaside. On the other hand, Cinnamomum japonicum, Ilex integra, and Camellia japonica grew wide range. And the heights of trees which found treelayer became higher as the landside.