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Abstract Background 2,3-Butanediol (2,3-BD), a valuable compound used for chemicals, cosmetics, pesticides and pharmaceuticals, has been produced by various microbes. However, no high-temperature fermentation of the compound at high productivity has been reported. Methods Thermotolerant xylose-utilizing microbes were isolated from 6 different districts in Laos and screened for a low accumulation of xylitol in a xylose medium at 37 ˚C. One isolate was found to produce 2,3-BD and identified by 16S rDNA sequencing. The 2,3-BD fermentation capacity was investigated at different temperatures using xylose and glucose as carbon sources, and the fermentation parameters were determined by a high-performance liquid chromatography system. Results By screening for a low accumulation of xylitol in a xylose medium, one isolate that accumulated almost no xylitol was obtained. Further analyses revealed that the isolate is Cronobacter sakazakii and that it has the ability to produce 2,3-BD at high temperatures. When xylose and glucose were used, this strain, named C. sakazakii OX-25, accumulated 2,3-BD in a short period before the complete consumption of these sugars and then appeared to convert 2,3-BD to acetoin. The optimum temperature of the 2,3-BD fermentation was 42 ˚C to 45 ˚C, and the maximum yield of 2,3-BD was 0.3 g/g at 12 h in 20 g/l xylose medium and 0.4 g/g at 6 h in 20 g/l glucose medium at 42 ˚C. The 2,3-BD productivity of the strain was higher than the 2,3-BD productivities of other non-genetically engineered microorganisms reported previously, and the highest productivity was 0.6 g/l·h and 1.2 g/l·h for xylose and glucose, respectively. Conclusions Among thermotolerant microbes isolated in Laos, we discovered a strain, C. sakazakii OX-25, that can convert xylose and glucose to 2,3-BD with high efficiency and high productivity at high temperatures, suggesting that C. sakazakii OX-25 has the potential for industrial application to produce 2,3-BD as an important platform chemical.

Candida tropicalis, a xylose-fermenting yeast, has the potential for converting cellulosic biomass to ethanol. Thermotolerant C. tropicalis X-17, which was isolated in Laos, was subjected to repetitive long-term cultivation with a gradual increase in temperature (RLCGT) in the presence of a high concentration of glucose, which exposed cells to various stresses in addition to the high concentration of glucose and high temperatures. The resultant adapted strain demonstrated increased tolerance to ethanol, furfural and hydroxymethylfurfural at high temperatures and displayed improvement in fermentation ability at high glucose concentrations and xylose-fermenting ability. Transcriptome analysis revealed the up-regulation of a gene for a glucose transporter of the major facilitator superfamily and genes for stress response and cell wall proteins. Additionally, hydropathy analysis revealed that three genes for putative membrane proteins with multiple membrane-spanning segments were also up-regulated. From these findings, it can be inferred that the up-regulation of genes, including the gene for a glucose transporter, is responsible for the phenotype of the adaptive strain. This study revealed part of the mechanisms of fermentability at high glucose concentrations in C. tropicalis and the results of this study suggest that RLCGT is an effective procedure for improving multistress tolerance.

Herbarium material collected in 2013–2015 in Cambodia and Laos provides 298 new localities for 167 orchid species (from 57 genera). Almost all reported locations are new on the territory of studied countries. These data provide substantial basis for understanding of present day distribution of rare species needed protection. Among reported species, 8 species are new for the flora of Cambodia (Bulbophyllum macranthum, B. orientale, B. physocoryphum, B. retusiusculum, Dendrobium pachyphyllum, Eria tenuiflora, Pholidota recurva, Thelasis pygmaea) and 43 species are new for the flora of Laos (Bulbophyllum ambrosia, B. andersonii, B. bicolor, B. bisetoides, B. delitescens, B. depressum, B. forrestii, B. lilacinum, B. longibrachiatum, B. psyhoon, Calanthe alismifolia, C. sylvatica, Cheirostylis pusilla, Cleisostoma melanorachis, C. subulatum, C. williamsonii, Coelogyne eberhardtii, C. leucantha, C. ovalis, Dendrobium eriiflorum, D. falconeri, D. trantuanii, D. williamsonii, Didymoplexis pallens, Epigeneium fuscescens, Eria apertiflora, E. bambusifolia, E. pachyphylla, Flickingeria fimbriata, Gastrochilus suavis, Liparis mannii, L. sootenzanensis, Luisia ramosii, Oberonia kwangsiensis, O. maxima, Pelatantheria insectifera, Phalaenopsis braceana, Pholidota yunnanensis, Schoenorchis scolopendria, S. tixieri, Tainia cordifolia, Thrixspermum calceolum). Five species (Dendrobium minusculum, Oberonia simplex, Porpax capuccinorum, P. laosensis and Taeniophyllum filiferum) discovered in Cambodia in Laos are described as new for science. One genus (Didymoplexis) was found in Laos at first. Such rare ornamental species as Aerides falcata, A. flabellata, A. rosea, Arundina caespitosa, Ascolabium pusillum, Bulbophyllum bicolor, Calanthe cardioglossa, Coelogyne assamica, C. calcicola, C. eberhardtii, C. flaccida, C. trinervis, Dendrobium aphyllum, D. christyanum, D. chryseum, D. chrysotoxum, D. crepidatum, D. dixanthum, D. falconeri, D. fimbriatum, D. findleyanum, D. gratiosissimum, D. jenkinsii, D. loddigesii, D. nobile, D. senile, D. thyrsiflorum, D. trantuanii, D. trigonopus, D. williamsonii, Doritis pulcherrima, Gastrochilus suavis, Holcoglossum kimballianum, H. subulifolium, Hygrochilus parishii, Paphiopedilum concolor, P. dianthum, Phalaenopsis braceana, Schoenorchis scolopendria, S. tixieri, Spathoglottis affinis, Tainia cordifolia, Vanda brunnea, V. denisoniana, V. flavobrunnea become presently very rare on the territory of studied local floras and badly need protection to prevent their extinction in nature.

The article presents a study concerning the new species of Isoëtes found in Laos. It says that the new species that were collected from the Nagang village, Laos were examined in terms of morphological characteristics and compared it to other species of Isoëtes for delimitation. The results showed that the new species differ from the other recorded species in terms of corm lobes, peripheral fibers, and velum. The researchers proposed to name the species Isoëtes laosienses.