Biohydrogen production by Thermoanaerobacterium thermosaccharolyticum KKU-ED1: Culture conditions optimization using mixed xylose/arabinose as substrate

Background: Biological hydrogen production by microorganisms can be divided into two main categories i.e. photosynthetic organisms that produce hydrogen using light as energy source and anaerobic bacteria that produce hydrogen via dark fermentation. Dark fermentative hydrogen production by anaerobic bacteria has the advantages of a higher HPR without illumination and of the capability to convert various kinds of substrate. Results: Thermophilic hydrogen producer was isolated from elephant dung and identified as Thermoanaerobacterium thermosaccharolyticum KKU-ED1 by 16S rRNA gene analysis, which was further used to produce hydrogen from mixed pentose sugar i.e., xylose/arabinose. The optimum conditions for hydrogen production from mixed xylose/arabinose by KKU-ED1 were a 1:1 xylose/arabinose mixture at the total concentration of 5 g/L, initial pH of 6.5 and temperature of 55ºC. Under the optimum conditions, hydrogen from sugar derived from acid-hydrolyzed sugarcane bagasse at a reducing sugar concentration were achieved. Soluble metabolite product (SMP) was predominantly acetic acid indicating the acetate-type fermentation. Conclusions: The strain KKU-ED1 appeared to be a suitable candidate for thermophilic fermentative hydrogen production from hemicellulosic fraction of lignocellulosic materials due to its ability to use various types of carbon sources.

Advances in and challenges for thermophilic fermentation of cellulosic ethanol / 生物工程学报

Thermophiles can produce cellulosic ethanol at a high temperature where ethanol is directly distillated from fermentation, and biodegradation of lignocellulose can be simultaneously achieved when these thermophiles carry and express cellulase and hemicellulase genes. The simultaneous biodegradation, fermentation and distillation, a three-in-one process, can result in low production costs of cellulosic ethanol. We reviewed the advances and challenges in the approach to the three-in-one process, which refer to lignocellulases, regulation mechanisms, and genetic transfer systems.

The product specificity evolution of cyclodextrin glucanotransferase: problems and challenges / 生物工程学报

Cyclodextrin glucanotransferase, the essential enzyme for the production of cyclodextrins, has become the focus of scientific research nowadays. Although many related enzyme properties are well known, the crucial factors in product specificity determination remain to be answered. Here, the recent research progresses of cyclodextrin glucanotransferase, especially those about the evolution of product specificity, were reviewed, and the scientific problems were discussed.