L-Alanine has important applications in food, pharmaceutical and veterinary and is used as a substrate for production of engineered thermoplastics. Microbial fermentation could reduce the production cost and promote the application of L-alanine. However, the presence of L-alanine significantly inhibit cell growth rate and cause a decrease in the ultimate L-alanine productivity. For efficient L-alanine production, a thermo-regulated genetic switch was designed to dynamically control the expression of L-alanine dehydrogenase (alaD) from Geobacillus stearothermophilus on the Escherichia coli B0016-060BC chromosome. The optimal cultivation conditions for the genetically switched alanine production using B0016-060BC were the following: an aerobic growth phase at 33 °C with a 1-h thermo-induction at 42 °C followed by an oxygen-limited phase at 42 °C. In a bioreactor experiment using the scaled-up conditions optimized in a shake flask, B0016-060BC accumulated 50.3 g biomass/100 g glucose during the aerobic growth phase and 96 g alanine/100 g glucose during the oxygen-limited phase, respectively. The L-alanine titer reached 120.8 g/l with higher overall and oxygen-limited volumetric productivities of 3.09 and 4.18 g/l h, respectively, using glucose as the sole carbon source. Efficient cell growth and L-alanine production were reached separately, by switching cultivation temperature. The results revealed the application of a thermo-regulated strategy for heterologous metabolic production and pointed to strategies for improving L-alanine production.

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The repetition of a stimulus often produces a shorter subjective duration than does the presentation of a novel item. To test whether familiarity mediates the repetition compression effect, the present study compared the influence of repeated words and pseudowords on apparent duration, using a duration discrimination task. We found a similar magnitude of temporal compression for the repeated-word and repeated-pseudoword conditions. When introducing a further experiment with two new conditions in which the standard-comparison pair shared a character at the first or second constituent position, we observed a shorter subjective duration for whole word (or whole pseudoword) repetition compared with the remaining conditions (i.e., first-character repetition, second-character repetition, and novel baseline). However, temporal compression for the first-and second-character repetitions was observed only for pseudowords but not for words. Our findings indicate that familiarity modulates the perception of duration in constituent character repetition. The results are discussed on the basis of the predictive coding theory.

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