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A high precision high-order curvature-compensated bandgap reference (BGR) compatible with standard BiCMOS process is presented in this paper that is capable of working down to input voltages of 1.6 V with 1.285 V output voltage. High-order curvature correction for this reference is accomplished by a novel piecewise technique, which realizes exponential curvature compensation in temperature range, and a logarithmic compensation term proportional to in higher temperature range through simple structures. Experimental results of the proposed BGR implemented in 0.5-m BiCMOS process demonstrate that a temperature coefficient (TC) of 5 ppm/ C is realized at 3.6 V power supply, a power-supply noise attenuation (PSNA) of 70 dB is achieved without filtering capacitors, and the line regulation is better than 0.47 mV/V from 1.6 V to 5 V supply voltage while dissipating a maximum supply current of 25 A. The active area of the presented BGR is 180 m 220 m.

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BackgroundCellulosic biomass especially agricultural/wood residues can be utilized as feedstock to cost-effectively produce fuels, chemicals and bulk industrial enzymes, which demands xylose utilization from microbial cell factories. While previous works have made significant progress in improving microbial conversion of xylose into fuels and chemicals, no study has reported the engineering of efficient xylose utilizing protein expression systems for the purpose of producing industrial enzymes.ResultsIn this work, using Pichia pastoris as an example, we demonstrated the successful engineering of xylose metabolizing ability into of protein expression systems. A heterologous XI (xylose isomerase) pathway was introduced into P. pastoris GS115 by overexpressing the Orpinomyces spp. XI or/and the endogenous XK (xylulokinase) gene, and evolutionary engineering strategies were also applied. Results showed that the XI pathway could be functionally expressed in P. pastoris. After 50 generation of sequential batch cultivation, a set of domesticated recombinant P. pastoris strains with different performance metrics on xylose were obtained. One evolved strain showed the highest xylose assimilation ability, whose cell yield on xylose can even be comparable to that on glucose or glycerol. This strain also showed significantly increased β-mannanase production when cultured on xylose medium. Furthermore, transcription analysis of xylose pathway genes suggested that overexpression of XI and XK might be the key factors affecting effective xylose assimilation.ConclusionsTo our best knowledge, this study is the first work demonstrating the construction of efficient xylose utilizing P. pastoris strains, thus providing a basis for using cellulosic biomass for bulk industrial enzyme production.