Artificial Neural Network Modeling of Mixing Efficiency in a Split-Cylinder Gas-Lift Bioreactor for Yarrowia lipolytica Suspensions

The mixing efficiency in a split-cylinder gas-lift bioreactor has been analyzed for Yarrowia lipolytica cells suspensions. Based on the experimental results, three different approaches for modeling have been applied to predict the mixing time depending on yeast concentration, aeration rate, as well as position on the riser or downcomer regions height. These approaches are represented by: an algorithm mixing differential evolution (DE) with artificial neural networks (ANNs), named hSADE-NN, regression, and the Multilayer Perceptron module from IBM SPSS. In the hSADE-NN, ANN models the process, while DE simultaneously optimizes the topology and the internal parameters of the ANN, so that an optimal model is obtained. It was found from simulations that ANNs are able to model the targeted process with a high degree of efficiency (average absolute relative error less than 8.5%), a small difference among the two ANN-based approaches being observed. Additionally, a sensitivity analysis was performed for determining the model inputs influence on the mixing time.     

Yarrowia lipolytica

The yeast Yarrowia lipolytica presents specific physiological, metabolic and genomic characteristics, which differentiate it from the model yeast Saccharomyces cerevisiae. These properties have led several research groups to use this yeast as a model for basic knowledge. Thanks to the development of advanced genetic tools and ‐omic approaches, significant progress has been achieved in the understanding of specific biological processes. This review, after a short presentation of this model yeast, will briefly highlight the different use of Y. lipolytica for basic knowledge and the advantages gained by exploiting this non‐conventional yeast. Future perspectives in employing this yeast for basic knowledge in the field of RNA splicing and genome evolution, and for the study of lipid metabolism, are also discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Application of a New Engineered Strain of Yarrowia lipolytica for Effective Production of Calcium Ketoglutarate Dietary Supplements

The present study aimed to develop a technology for the production of dietary supplements based on yeast biomass and α-ketoglutaric acid (KGA), produced by a new transformant of Yarrowia lipolytica with improved KGA biosynthesis ability, as well to verify the usefulness of the obtained products for food and feed purposes. Transformants of Y. lipolytica were constructed to overexpress genes encoding glycerol kinase, methylcitrate synthase and mitochondrial organic acid transporter. The strains were compared in terms of growth ability in glycerol- and oil-based media as well as their suitability for KGA biosynthesis in mixed glycerol–oil medium. The impact of different C:N:P ratios on KGA production by selected strain was also evaluated. Application of the strain that overexpressed all three genes in the culture with a C:N:P ratio of 87:5:1 allowed us to obtain 53.1 g/L of KGA with productivity of 0.35 g/Lh and yield of 0.53 g/g. Finally, the possibility of obtaining three different products with desired nutritional and health-beneficial characteristics was demonstrated: (1) calcium α-ketoglutarate (CaKGA) with purity of 89.9% obtained by precipitation of KGA with CaCO₃, (2) yeast biomass with very good nutritional properties, (3) fixed biomass-CaKGA preparation containing 87.2 μg/g of kynurenic acid, which increases the health-promoting value of the product.     

菊粉酶基因克隆表达与油脂的组分分析

为了实现解脂亚罗威亚酵母（Yarrowia lipolytica）直接利用菊粉进行油脂生产,将外切菊粉酶基因INU1与表达质粒pINA1317连接,在解脂亚罗威亚酵母（Y. lipolytica）ACA-DC尿嘧啶缺陷突变菌株中表达。以尿嘧啶缺陷型筛选作为筛选标记获得转化子C37,经过培养菊粉酶酶活达到37.15 U/mL。在2 L发酵罐中,转化子C37以菊粉为底物进行发酵,油脂产量和细胞干质量分别为49%和14 g/L。脂肪酸分析结果显示棕榈酸、硬脂酸和油酸总和占总脂肪酸的92%以上,其中油酸含量高达59%,表明通过菊粉酶基因在解脂亚罗威亚酵母中的表达,实现了以菊粉为底物一步发酵产单细胞油脂。     

野生山毛豆蛋白制备及体外消化模拟研究

通过碱提酸沉法制备野生山毛豆蛋白,并模拟人体消化环境,采用胃蛋白酶、胰蛋白酶两步消化法分析山毛豆蛋白的消化行为。结果表明：山毛豆中蛋白质含量约为(47.12 ± 0.35)%,大豆中蛋白质含量约为(44.17 ±0.48)%,山毛豆含有18 种氨基酸,其中包括人体必需的8 种氨基酸,从非必需氨酸酸来看,山毛豆蛋白与大豆蛋白有相似的氨基酸组分,氨基酸平衡状况较好,接近参考蛋白模式;山毛豆的体外消化率为(84.86 ± 0.75)%,大豆的体外消化率为(91.71 ± 0.88)%,山毛豆酶解液中的总氨基酸含量比大豆的略低,但山毛豆酶解液中甘氨酸和色氨酸含量比大豆酶解液高很多,游离氨基酸(FAA)含量比大豆的略高。     

Effect of Citrus essential oil addition upon growth and cellular lipids of Yarrowia lipolytica yeast

The chemical composition of the essential oil from fruits of the Greek citrus hybrid Citrus sinensis cv New Hall – Citrus aurantium was investigated by GC and GC-MS. Forty-four compounds were identified, representing 92.83% of the total oil. Limonene, myrcene, β-pinene, α-pinene and α-terpineol constituted the major components of the oil. The effect of the addition of this oil upon the behavior of Yarrowia lipolytica yeast was also investigated. The microorganism was aerobically grown on glucose and oil was added to the culture medium in various initial quantities (from 0.0 to 1.5 mL/L). The strain underwent significant inhibition exerted by the added essential oil; a decrease of the highest achieved biomass concentration, even if the oil was added to the culture medium at small concentrations (e.g. 0.3 mL/L), was observed. The more oil was added, the more the lag phase of the growth increased, while the biomass yield on glucose consumed decreased with the addition of the oil. When the essential oil was added to the medium, even at small concentrations, a significant increase of cellular medium-chain saturated fatty acids (12:0 and 14:0) resulting in an increase of saturated fatty acid content in the cellular lipids, was observed.     

A comprehensive study of lipase production by Yarrowia lipolytica CECT 1240 (ATCC 18942): from shake flask to continuous bioreactor

BACKGROUND: Lipases are commercially important enzymes, and the development and optimization of their production processes are of great interest. The diversity of behaviours between strains stresses the need for research on this topic, especially when bioreactor culture is considered. The study of a continuous operating mode is especially attractive, since very scarce information is available on its application to microbial lipases production. RESULTS: Lipase production in submerged cultures of Yarrowia lipolytica CECT 1240 (ATCC 18 942) has been investigated. Significant lipolytic activity (over 700 U dm^?3), mostly extracellular and membrane‐bound, was obtained in shake flasks using medium supplemented with olive oil. The culture was carried out in air‐lift and stirred tank bench‐scale bioreactors and the latter was selected. The influence of aeration and agitation rates was assessed in batch cultures, and agitation from 400–700 rpm and low aeration rates (i.e. 0.2 vvm) are recommended. Batch, fed‐batch and continuous operation were investigated, and regular enzyme production (up to 600 U dm^?3) was achieved with the latter. CONCLUSION: Lipase production by the selected strain was successfully carried out in shake flasks and bench‐scale bioreactors. After studying batch, fed‐batch and continuous processes, continuous culture in a stirred tank bioreactor was found best in terms of regular enzyme production, exceptionally good operational stability and good fitting of the results to mathematical models. Copyright © 2009 Society of Chemical Industry     

大孔吸附树脂分离纯化谷胱甘肽的初步研究

以产朊假丝酵母提取液作为试验样品进行了大孔吸附树脂sp-207对谷胱甘肽吸附性能的研究,得到分离纯化的最佳条件:上样pH2.0、流速0.5BV/h、70%甲醇解吸,流速1.0BV/h。在最佳条件下回收率78.84%。