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Abstract A suitable nutrient supply, especially of vitamins, is very significant for the deep display of the inherent genetic properties of microorganisms. Here, using the chemically defined minimal medium (MM) for yeast, nicotinamide and inositol were confirmed to be more beneficial for the performance of two industrial baker's yeasts, a conventional and a high-sugar-tolerant strain. Increasing nicotinamide or inositol to proper levels could enhance the both strains on cell growth and activity and product performance, including trehalose accumulation and leavening performance. The activity of key enzymes (PCK, TPS) and the content of intermediate metabolites (G6P, UDPG) in the trehalose synthesis pathway were promoted by a moderate supply of nicotinamide and inositol. That were also proved that an appropriate amount of niacinamide promoted the transcription of longevity-related genes (PNC1, SIR2), and the proper concentration of inositol altered the phospholipid composition in cells, namely, phosphatidylinositol and phosphatidyl choline. Furthermore, the cell growth and the leavening performance of the both strains were promoted after adjusting inositol to choline to the proper ratio, resulting directly in content changes of phosphatidylinositol and phosphatidyl choline in the cells. While the two strains responded to the different proper ratio of inositol to choline probably due to their specific physiological characteristics. Such beneficial effects of increased nicotinamide levels were confirmed in natural media, molasses and corn starch hydrolyzed sugar media. Meanwhile, such adjustment of inositol to choline ratio could lessen the inhibition of excess inositol on cell growth of the two tested strains in corn starch hydrolyzed sugar media. However, in molasse, such phenomenon was not observed probably since there was higher Ca2+ in it. The results indicated that the effects of nutrient factors, such as vitamins, on cell growth and other properties found out from the simple chemically defined minimal medium were an effective measure to use in improving the recipe of natural media at least for baker's yeast.

Rate-distortion optimization (RDO) is a crucial technique in block-based hybrid video encoders, which determines the coding option for a certain coding unit to achieve optimal rate-distortion (R-D) performance. However, the current RDO, which is implemented into High Efficiency Video Coding (HEVC) test model, i.e., HM, is far from being global optimal as it ignores the interaction among coding options. Recent studies have shown that the dependent RDO methods can improve the coding efficiency of encoders by exploring the R-D dependency among coding units, but these methods do not consider the R-D characteristics of coding units. In this paper, we proposed a two-pass encoding based RDO method, which combines both the R-D dependency and R-D characteristics, to further improve the coding efficiency. First, a frame is encoded with the original HEVC scheme to obtain the R-D model of coding tree units (CTU) and the bit budget of the frame. Second, an optimal equation combines the R-D model and R-D dependency is established to adaptively determine the Lagrange multiplier and quantization parameter (QP) for each CTU. Finally, the current frame is encoded with a new scheme again. Experimental results show that compared with the original HM, the proposed method obtains R-D performance improvements of 5.3% and 5.6% on average under configurations of low-delay B and P frames, respectively.