Poly-γ-glutamic acid (γ-PGA) is an emerging biopolymer with various applications and γ-PGAs with different molecular weights exhibit distinctive properties. However, studies on the controllable molecular weights of biopolymers are limited. The purpose of this study is to achieve production of γ-PGAs with a wide range of molecular weights through manipulating the expression of γ-PGA depolymerase (PgdS) in Bacillus licheniformis WX-02. Firstly, the expression and secretion of PgdS were regulated through engineering its expression elements (four promoters and eight signal peptides), which generated γ-PGAs with molecular weights ranging from 6.82 × 10 4 to 1.78 × 10 6 Da. Subsequently, through combination of promoters with signal peptides, the production of γ-PGAs with a specific molecular weight could be efficiently obtained. Interestingly, the γ-PGA yield increased with the reduced molecular weight in flask cultures (Pearson correlation coefficient of −0.968, P < 0.01). Finally, in batch fermentation, the highest yield of γ-PGA with a weight-average molecular weight of 7.80 × 10 4 Da reached 39.13 g/L under glutamate-free medium. Collectively, we developed an efficient strategy for one-step production of γ-PGAs with specific molecular weights, which have potential application for industrial production of desirable γ-PGAs.

Acrylamide (AA) is known to be a neurotoxic, genotoxic and carcinogenic compound, which is classified as a probable human carcinogen. The main purpose of this paper was to study the changes in peroxide value (PV), p-anisidine value (PAV), methylglyoxal (MG), and moisture content (MC) in potato slices fried at different temperatures and lengths of time. The determination of AA was carried out using HPLC-MS/MS.Our results showed that AA formation was obviously influenced by MG content and PV; the AA content increases with the increase of PV and MG. The contribution of PV and MG to AA formation was included in a prediction model that could be used as a tool to predict the formation of AA in potato slices, and the model was as follows: AA ¼ À0.200-0.001 Â MC + 0.330 Â PV + 0.074 Â PAV + 0.103 Â MG. The predicted AA content value was in good agreement with the actual AA content.

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With the development of mobile communication technology, there are more and more concern about the mobile cyber security. However, numerous existing authentication solutions have the issues as encryption and decryption keys long, slow, consuming large storage space and transmission bandwidth. This article presents an approach based on elliptic curve cryptography is suitable for the identity of the mobile terminal lightweight equipment certification program, which improve efficiency, while reducing the bandwidth consumption of transmission. Therefore, the solution has a great potentiality in the application of intelligent terminal.

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