Sediment phosphorus speciation and retention process affected by invasion time of Spartina alterniflora in a subtropical coastal wetland of China.

In coastal wetland ecosystems, most phosphorus (P) accumulates in the sediments and becomes a major pollutant causing eutrophication by recycling to the water column in estuary areas, especially exotic plant invasions will change the nutrient cycling. In this study, a large wetland invaded by exotic species Spartina alterniflora for over 15 years was selected to study the sediment P fractionation and its retention for different plant invasion periods. The samples were collected from east to west in September and the sediment P was fractionated into total P (TP), inorganic P (IP), iron/aluminum-bound P (Fe/Al-P), calcium-bound P (Ca-P), and organic P (OP). Additionally, the effect of the invasion period on the wetland P fractionation based on space-time reciprocal principle was investigated. For different S. alterniflora invasion periods, the average TP concentration was 675.37 mg kg-1 with a range of 160.33-1071 mg kg-1. The IP concentration was in the range of 107.33-813.33 mg kg-1 (accounting for 54.4-79.5% of TP), of which Fe/Al-P and Ca-P represented up to 99.4%. In addition, the P retention (RP) was within 41.67-329.67 mg kg-1. We also found that TP, IP, Fe/Al-P, Ca-P, OP, and RP in sediments were negatively correlated with pH (p < 0.05), and were also significantly positively correlated (p < 0.01) with water content and electrical conductivity. There were positive correlations between the various forms of P in the sediments (p < 0.01). However, the most important finding was that invasion time of S. alterniflora had a direct effect on the P speciation and three stages were determined. In the first stage, S. alterniflora mainly consumed the OP of the sediment. In the second stage, S. alterniflora showed great vitality and biological immobilization led to the transforming of IP to OP. In the third stage, all P fractions greatly decreased to values even lower than for the bare beach which indicated that S. alterniflora growth had begun to degenerate. These three stages well explained the P seemingly contradictory increases and decreases apparent in previous studies and provide important information for understanding the effect of S. alterniflora invasion.

Enhanced production of triterpenoid in submerged cultures of Antrodia cinnamomea with the addition of citrus peel extract.

In recent years, Antrodia cinnamomea has become a well-known medicinal mushroom in Taiwan. Triterpenoids are considered one of the most biologically active components found in A. cinnamomea. The aim of this research is to investigate the feasibility of enhancing triterpenoid production in shake flask cultures of A. cinnamomea by adding citrus peel extract. As a result of its containing essential oils, citrus peel extract is inhibitory to mycelial growth. In the experiments, the appropriate adding time is determined to be on day 7. Of the various citrus peel extracts tested, tangerine proves to be the most effective in enhancing polyphenol and triterpenoid production. With an addition of 2% (v/v), the content and production of total polyphenols rises from 5.95 mg/g DW of the control and 56.73 mg/L to 23.52 mg/g DW and 224.39 mg/L, respectively, on day 28. The production of triterpenoids also increases from 99.93 to 1,028.02 mg/L, for more than a tenfold increase. An optimal level of tangerine peel additive is determined to be around 4%. Furthermore, when compared with the mycelia of the control culture, the profiles of the HPLC analysis show that the mycelia cultured with the tangerine-peel addition contain more kinds of triterpenoids. This study demonstrates that the addition of citrus peel extract effectively enhances the production of bioactive metabolites in the submerged cultures of A. cinnamomea.