Towards semi-synthetic microbial communities: Enhancing soy sauce fermentation properties in B. subtilis co-cultures

Background Many fermented foods and beverages are produced through the action of complex microbial communities. Synthetic biology approaches offer the ability to genetically engineer these communities to improve the properties of these fermented foods. Soy sauce is a fermented condiment with a vast global market. Engineering members of the microbial communities responsible for soy sauce fermentation may therefore lead to the development of improved products. One important property is the colour of soy sauce, with recent evidence pointing to a consumer preference for more lightly-coloured soy sauce products for particular dishes. Results Here we show that a bacterial member of the natural soy sauce fermentation microbial community, Bacillus, can be engineered to reduce the ‘browning’ reaction during soy sauce production. We show that two approaches result in ‘de-browning’: engineered consumption of xylose, an important precursor in the browning reaction, and engineered degradation of melanoidins, the major brown pigments in soy sauce. Lastly, we show that these two strategies work synergistically using co-cultures to result in enhanced de-browning. Conclusions Our results demonstrate the potential of using synthetic biology and metabolic engineering methods for fine-tuning the process of soy sauce fermentation and indeed for many other natural food and beverage fermentations for improved products

Genetic variation among Amorphophallus sp. from Northern Thailand and their glucomannan content

This study investigated the genetic variations among different accessions of Amorphophallus sp. collected in northern regions of Thailand. Forty-tree samples were characterized by RAPD with four primers (ERIC1R, ERIC 2, BOXA1R, RPO1) the data from which were used to calculate genetic distances which were then visualized using multidimensional scaling and cladogram. The psbM-trnD region of their chloroplast genome was also sequenced and phylogenetic relationships were determined using parsimony analysis. In addition, glucomannan content was determined to find the relationship between genetic variation and glucomannan content. The results from the RAPD analysis show that the genetic distance values vary between 0.075 and 0.949 and that A. muelleri can be separated from A. paeoniifolius. However, the separation of the other species was ambiguous. The DNA sequence data suggested the presence of 5 different clades. All genetic data indicated that genetic variation was high. Glucomannan content was between 1.53-65.78% (w/w) depending on the species and the regions of origin. As a result, these markers appear to be suitable for the use as selection tools aiming at improving the industrial production of konjac glucomannan

Determination of relationships and genetic variation among Amorphophallus sp. from northern part of Thailand

Amorphophallu sp. are known under the common name of konjac or elephant foot yam. Some of the species have potential to become highly profitable crops for South East Asia as raw material for various industries. However, considerable variation in morphological features of many species of Amorphophallus makes it is difficult to identify them in the vegetative form. Randomly Amplified Polymorphic DNA (RAPD) and DNA Sequencing are often used to determine the genetic relationship of plants. The aim of this study was to determine the relationship and genetic variation of various accessions of Amorphophallus sp. collected in northern regions of Thailand. Fifty samples were characterised by RAPD with four primers (ERIC1R, ERIC 2, BOXA1R, RPO1) the data from which were used to calculate genetic distances which were then visualized using multidimensional scaling. In addition, the psbM-trnD region of their chloroplast genome was also sequenced from which phylogenetic relationships were determined using parsimony analysis. The results from the RAPD analysis placed the accessions into 35 different groups with distance values between 0.075 and 0.949. The DNA sequence data found the accessions into 30 different groups. Further work will be carried out to more closely determine the relationships between the accessions and to relate them to each other