Objective: Thai medicinal plants were used as the traditional medicines and as part of everyday plants diet. Plants contain a mixture of phytochemical and exhibit a lot of functional food and medicinal properties. This project aims to investigate the potential of selected Thai medicinal plants according to the properties of their antioxidant and antibacterial activities. Methods: The eighteen plants were extracted using maceration method with 95% ethanol. The antioxidant activity was evaluated by DPPH and FRAP assay. The total phenolic content was evaluated by Folin-Ciocalteu phenol reagent. The antibacterial activity was evaluated by agar disc diffusion method. The extract which exhibited high antioxidant and antibacterial activity was selected to observe morphological changes by the scanning electron microscope (SEM). Results: The extract of Caesalpinia sappan showed the highest activities on both antioxidant assayed by FRAP method and total phenolic contents, however, exhibited high antioxidant assayed by DPPH compared to Bauhinia strychnifolia extract. Moreover, the extract of C. sappan showed the excellent antibacterial activities against six pathogenic bacteria in Gastro-intestinal tract. The morphological change by SEM was selected for further investigation antibacterial activities of C. sappan extract. The results showed that the inhibitory effect to those bacterial strains could be caused by the disruption of the cell membrane and decrease biofilm formation after treatment with the extract. Conclusion: The ethanol extract of C. sappan exhibited strong antioxidant and antibacterial activities against the six pathogenic bacteria. This result suggested that C. sappan could be applied to use for medicinal purpose and functional products. Key words: Antioxidant activity, Antibacterial activity, Total phenolic content, Caesalpinia sappan, Scanning electron microscope. 11,12,13 Previous studies showed the possibility to use many Thai plants as antioxidants and antibacterial agents. Some Thai plant extracts such as Cassia siamea, Garcinia cowa, Limnophila aromatica, Polygonum odoratum, Dioscorea bulbifera, Syzygium cumini and Zingiber zerumbet which have been reported for their antioxidant activities, and these plants also exhibit antibacterial against some pathogenic bacteria. 14,15,16,17 However, there are many medicinal Thai plants which are not to be evaluated their antioxidant related to antibacterial activities from GI tract. Due to the abovementioned facts, this project aims to investigate the potential of Thai plants according to the properties of the plant extracts on their antioxidant and antibacterial activities including their effects on morphological changes of selected pathogenic bacteria in GI tract. This information will be used as guide line for development of medicinal products and functional ingredients for use in novel functional food products. Parichat MATERIALS AND METHODS Sample collectionEighteen plant samples were selected based on Thai traditional medicine and their health pro...

Microalgae consortia were photoautotrophically cultivated in sequencing batch photobioreactors (SBPRs) with an alteration of the normal growth and starvation (nutrient limitation) phases to select consortia capable of polyhydroxyalkanoate (PHA) accumulation. At the steady state of SBPR operation, the obtained microalgae consortia, selected under nitrogen and phosphate limitation, accumulated up to 11.38% and 10.24% of PHA in their biomass, which was identified as poly(3-hydroxybutyrate) (P3HB). Photoautotrophic and mixotrophic batch cultivation of the selected microalgae consortia was conducted to investigate the potential of biomass and PHA production. Sugar source supplementation enhanced the biomass and PHA production, with the highest PHA contents of 10.94 and 6.2%, and cumulative PHA productions of 100 and 130 mg/L, with this being achieved with sugarcane juice under nitrogen and phosphate limitation, respectively. The analysis of other macromolecules during batch cultivation indicated a high content of carbohydrates and lipids under nitrogen limitation, while higher protein contents were detected under phosphate limitation. These results recommended the selected microalgae consortia as potential tools for PHA and bioresource production. The mixed-culture non-sterile cultivation system developed in this study provides valuable information for large-scale microalgal PHA production process development following the biorefinery concept.

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