Optimization of Riboflavin Production from ccpA Mutant Bacillus subtilis 24A1/pMX45

The nitrogen source requirements for riboflavin production by ccpA mutant Bacillus subtilis 24A1/pMX45 were optimized using linear regression. The optimal medium components considered included 8% glucose as carbon source, 2% yeast powder, 0.05% MgSO4 ·7H2O, and four types of nitrogen sources ： 0.1% yeast extract, 2% soybean powder, 1% corn plasm, and 0.2% （ NH4 ） 2 HPO4 in shake flask tests. Predictive ellipsoid was applied to determining the response values under the optimal levels for riboflavin production and glucose consumption. The optimal concentrations of the four types of nitrogen sources can remedy ammonium assimilative defection of ccpA mutant. Under the optimal conditions, the riboflavin yield increases to more than 5.0 g/L and 8%, glucose can be consumed completely after 60 h.

Global finite-time attitude regulation using bounded feedback for a rigid spacecraft

This paper investigates the problem of global attitude regulation control for a rigid spacecraft under input saturation. Based on the technique of finite-time control and the switching control method, a novel global bounded finite-time attitude regulation controller is proposed. Under the proposed controller, it is shown that the spacecraft attitude can reach the desired attitude in a finite time. In addition, the bound of a proposed attitude controller can be adjusted to any small level to accommodate the actuation bound in practical implementation.

Some Neglected Causes of the Global Financial Crisis and Their Implications for Effective Crisis Governance

The essay analyzes in a sociological and political science perspective several key aspects of the global economic-financial crisis which have either been neglected or not sufficiently analyzed in most scientific and media accounts. It focuses on two basic aspects： a） the coguitive framework prevailing among U. S. corporate, governmental and intellectual elites, i.e. the neodiberal conception of the self-regulating market, which deeply influenced their behaviour both in the market and in the political arena and b ） the mechanisms of pressure politics and political lobbying in the US Congress that managed to influence key decisions concerning de-regulation policy, in so far as to weaken the existing systems of institutional controls and to prevent new rules for new financial products. The last section evaluates President Obama＇s economic strategy and regulation policy in the light of the two basic aspects analysed in the first two sections, i.e. the action of lobbies and the influence of mainstream neo-hberal economics. The aim of the essay is to integrate the economic literature with a sociological and political analysis in order to gain clearer knowledge of the complex mechanisms of the crisis, which in turn can contribute to identifying key obstacles in implementing pohcies aimed at enforcing new forms of regulation of global markets.

Combinatorial metabolic engineering of Saccharomyces cerevisiae for improved production of 7-dehydrocholesterol

7-Dehydrocholesterol(7-DHC),a key pharmaceutical intermediate in the production of vitamin D3,has a wide range of applications.To explore fermentative synthesis of 7-DHC,a 7-DHC-producing Saccharomyces cerevisiae strain was constructed by blocking the competitive pathway,eliminating rate-limiting steps,altering global reg-ulation,and pathway compartmentalization.After blocking the competitive pathway by disrupting ERG5 and ERG6 and introducing DHCR24 from Gallus gallus,S.cerevisiae produced 139.72 mg/L(17.04 mg/g dry cell weight,hereafter abbreviated as DCW)7-DHC.Subsequent alteration of global regulation by deleting ROX1 and overexpressing UPC2-1 increased 7-DHC production to 217.68 mg/L(37.56 mg/g DCW).To remove the accu-mulated squalene,the post-squalene pathway was strengthened by co-overexpression of PGAL1-driven ERG11 and PGAL10-driven ERG1,which improved 7-DHC titer and yield to 281.73 mg/L and 46.78 mg/g DCW,respectively,and reduced squalene content by 90.12%.We surmised that the sterol precursors in the plasma membrane and peroxisomes may not be accessible to the pathway enzymes,thus we re-localized DHCR24p and Erg2p-GGGGS-Erg3p to the plasma membrane and peroxisomes,boosting 7-DHC production to 357.53 mg/L(63.12 mg/g DCW).Iron supplementation further increased 7-DHC production to 370.68 mg/L in shake flasks and 1.56 g/L in fed-batch fermentation.This study demonstrates the power of global regulation and subcellular relocalization of key enzymes to improve 7-DHC synthesis in yeast.

Engineering of Saccharomyces cerevisiae for co-fermentation of glucose and xylose:Current state and perspectives

The use of non-food lignocellulosic biomass to produce ethanol fits into the strategy of a global circular economy with low dependence on fossil energy resources.Xylose is the second most abundant sugar in lignocellulosic hydrolysate,and its utilization in fermentation is a key issue in making the full use of raw plant materials for ethanol production and reduce production costs.Saccharomyces cerevisiae is the best ethanol producer but the organism is not a native xylose user.In recent years,great efforts have been made in the construction of xy-lose utilizing S.cerevisiae strains by metabolic and evolutionary engineering approaches.In addition,managing global transcriptional regulation works provides an effective means to increase the xylose utilization capacity of recombinant strains.Here we review the common strategies and research advances in the research field in order to facilitate the researches in xylose metabolism and xylose-based fermentation.

Paradox of international maritime organization's carbon intensity indicator

The 76th session of the Marine Environment Committee(MEPC 76)of the International Maritime Organization adopted several mandatory measures in June 2021 to reduce carbon emissions from ships.One of the measures is the carbon intensity indicator(CII),which is the carbon emissions per unit transport work for each ship.Several options of CIIs are available and none of them is chosen to be applied yet.We prove that,at least in theory,requiring the attained annual CII of a ship to be less than a reference value,no matter which CII option is applied,may increase its carbon emissions.Therefore,more elaborate models,combined with real data,should be developed to analyze the effectiveness of each CII option and possibly to design a new CII.