Previous studies from our laboratory have indicated that audible sound field stimulation can significantly affect E.coli growth and metabolic action, which can enhance or inhibit the growth of Escherichia coli (E.coli), and the effects of sound field on E.coli growth depended greatly on the intensity and frequency of sound field. However, very little efforts have been put forth in studying the potential mechanism of bacterial cells responses to audible sound stimulation. In this paper, the potential role of calcium signaling in mediating the response of E.coli to audible sound stimulation was firstly reported. We found that audible sound wave stimulation could evidently enhance total intracellular Ca2+ content. And the lack of calcium ion in medium significantly alleviated audible sound wave biological effects. Moreover, by adding appropriate level of calcium chloride to the LB medium contained 1.2 mM EDTA, the promotion effect of audible sound wave to E.coli growth was gradually resumed. On the basis of these findings, we speculate that calcium signaling may play an important role in mediating the response of E.coli to audible sound stimulation.
In order to obtain an industrial strain with higher xylanase production, the original strain of Aspergillus niger was mutated by N + implantation (10 keV, 1.04 · 10 15 -2.08 · 10 15 ions/cm 2 ), and a mutant P602 was obtained. The mutant showed xylanase production increased from 2989 to 6320 IU/g and the fermentation time was decreased from 72 h to 64 h. The fermentation temperature range was 28-32°C which was a little wider than the original strain.
With ion implantation, a high xylanase-producing strainAspergillus nigerBU99 was selected. Different late acting carbon sources (wheat bran, wheat straw, corncob and bagasse) had an effect on enzymatic production. Additionally, it was found that fast acting carbon sources (lactose, galactose, sucrose, glucose and maltose) put into the media affected on xylanase production too. Severe catabolic repression was observed in the media with lactose, but other sugars (galactose, sucrose, glucose and maltose) could increase the production of xylanase compared with the control. The production of xylanase was improved too when corncob flour was hydrolyzed by α-amylase, cellulase or/and glucoamylase. Additionally, it was found that the production of xylanase would be almost higher at 60h when the media contained glucose or were hydrolyzed by enzymes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.