Following the rising concern on environmental issues caused by conventional fossil-based plastics and depleting crude oil resources, polyhydroxyalkanoates (PHAs) are of great interest by scientists and biodegradable polymer market due to their outstanding properties which include high biodegradability in various conditions and processing flexibility. Many polyhydroxyalkanoate-synthesizing microorganisms, including normal and halophilic bacteria, as well as algae, have been investigated for their performance in polyhydroxyalkanoate production. However, to the best of our knowledge, there is still limited studies on PHAs-producing marine yeast. In the present study, a halophilic yeast strain isolated from Spratly Island in Vietnam were investigated for its potential in polyhydroxyalkanoate biosynthesis by growing the yeast in Zobell marine agar medium (ZMA) containing Nile red dye. The strain was identified by 26S rDNA analysis as Pichia kudriavzevii TSLS24 and registered at Genbank database under code OL757724. The amount of polyhydroxyalkanoates synthesized was quantified by measuring the intracellular materials (predicted as poly(3-hydroxybutyrate) -PHB) by gravimetric method and subsequently confirmed by Fourier transform infrared (FTIR) spectroscopic and nuclear magnetic resonance (NMR) spectroscopic analyses. Under optimal growth conditions of 35 °C and pH 7 with supplementation of glucose and yeast extract at 20 and 10 gL⁻¹, the isolated strain achieved poly(3-hydroxybutyrate) content and concentration of 43.4% and 1.8 gL⁻¹ after 7 days of cultivation. The poly(3-hydroxybutyrate) produced demonstrated excellent biodegradability with degradation rate of 28% after 28 days of incubation in sea water.

This article reports on the ability of yeast Trichosporon asahii B1 biofilm-associated cells, compared with that of planktonic cells, to transform sec-hexylbenzene and its metabolites. This B1 strain was isolated from a petroleum-polluted sediment collected in the QuangNinh coastal zones in Vietnam, and it can transform the branched aromatic hydrocarbons into a type of forming biofilm (pellicle) more efficiency than that the planktonic forms can. In the biofilm cultivation, seven metabolites, including acetophenone, benzoic acid, 2,3-dihydroxybenzoic acid, β-methylcinnamic acid, 2-phenylpropionic acid, 3-phenylbutyric acid, and 5-phenylhexanoic acid were extracted by ethyl acetate and analyzed by HPLC and GC-MS. In contrast, in the planktonic cultivation, only three of these intermediates were found. An individual metabolite was independently used as an initial substrate to prove its degradation by biofilm and planktonic types. The degradation of these products indicated that their inoculation with B1 biofilms was indeed higher than that observed in their inoculation with B1 planktonic cells. This is the first report on the degradation of sec-hexylbenzene and its metabolites by a biofilm-forming Trichosporon asahii strain. These results enhance our understanding of the degradation of branched-side-chain alkylbenzenes by T. asahii B1 biofilms and give a new insight into the potential role of biofilms formed by such species in the bioremediation of other recalcitrant aromatic compounds.

Nowadays, polyhydroxyalkanoates (PHAs) is of great interest by scientists and biodegradable polymer market due to their outstanding properties such as high biodegradability in various conditions and processing flexibility. Many PHAs-synthesizing microorganisms, including normal and halophilic bacteria, and algae, were investigated. However, to the best of our knowledge, there is still little studies on PHAs-producing marine yeast. In the present study, a halophilic yeast strain isolated from Spratly Island in Vietnam were investigated for synthesis of PHA by growing the yeast in a specific medium containing Nile red dye. The strain was identified by 26S rDNA analysis as Pichia kudriavzevii TSLS24 and registered at Genbank database under code OL757724. The amount of PHA synthesized was quantified by measuring the intracellular materials (predicted as PHA) by gravimetric method, subsequently confirmed by Fourier transform infrared spectroscopic and nuclear magnetic resonance spectroscopic analyses. Under optimal growth conditions of 35 ^oC and pH 7 with supplementation of glucose and yeast extract at 20 and 10 g/L, the strain isolated achieved PHA content and concentration of 43.4% and 1.8 g/L. Degradation rate of PHA produced was 28% after 28 days of incubation in sea water.