Hongmei Yao

Variations and modelling of oxygen demand in amino acid production

Abstract The l -lysine fermentation by Brevibacteria lactofermentum was investigated in this study. The objective was to improve the process performance by manipulating cellular environment conditions. The main factor under consideration was dissolved oxygen concentration (DOC) in the broth. To implement effective process control, a process model was developed based on combined kinetic study and material balances. The process dynamics at the dissolved oxygen tensions (DOTs) of 2%, 5%, 10%, and 20% was analysed. The results showed that inhibition of high oxygen level could occur during the very early growth phase and depressive effect of low oxygen availability was confined to the rest of the process, suggesting that different fermentation stages required different DOTs. Batch experiments were conducted with 3% DOT for the first 24 h, 10% for 24–48 h, and 5% for the rest of the fermentation, and the results were compared with those under 20% DOT throughout. The final l -lysine concentration reached 51.4 g/l compared with 45 g/l; the overall yield increased from 0.300g/g to 0.343g/g; and the productivity was improved from 0.616 g/l/h to 0.643 g/l/h. Also importantly, the low DOT settings required much less energy for agitation and aeration.

Continuous prediction technique for fast determination of cyclic steady state in simulated moving bed process

National Natural Science Foundation of China [20876128, 21206118]; Fundamental Research Funds for the Central Universities [2010121049]

Study on the number of decision variables in design and optimization of Varicol process

Abstract As a variant of simulated moving bed chromatography, Varicol process can realize flexible adsorbent allocation through asynchronous shifting of inlet and outlet ports. In this research, the switching strategies for achieving one certain average configuration were investigated. It was found the system performance depends on the total number of switches of the four ports during one switching period and Simple-Shifting-Scheme (SSS) with four switches brings out the best performance. More importantly, SSS could be different schemes, different by a parallel shifting, but all of them result in the same performance, demonstrating that only three instead of four switching times are decision variables while designing a Varicol process. To make the design of SSS more solid, a systematic method for derivation of SSS is proposed and applied on the optimization of a Varicol process for enantioseparation of 1,1′-bi-2-naphthol and reduce the solvent consumption by 17% comparing with SMB.

Computation of Mathematical Models for Complex Industrial Processes

Designed for undergraduate and postgraduate students, academic researchers and industrial practitioners, this book provides comprehensive case studies on numerical computing of industrial processes and step-by-step procedures for conducting industrial computing. It assumes minimal knowledge in numerical computing and computer programming, making it easy to read, understand and follow. Topics discussed include fundamentals of industrial computing, finite difference methods, the Wavelet-Collocation Method, the Wavelet-Galerkin Method, High Resolution Methods, and comparative studies of various methods. These are discussed using examples of carefully selected models from real processes of industrial significance. The step-by-step procedures in all these case studies can be easily applied to other industrial processes without a need for major changes and thus provide readers with useful frameworks for the applications of engineering computing in fundamental research problems and practical development scenarios.

Preparation of a Monolith with Covalently Bound Bovine Serum Albumin for Capillary Electrochromatography

Capillary electrochromatography (CEC) is important for applications in enantiomer separation. The problems associated with column fabrication bring a challenge in developing monoliths with ease of preparation, robustness of separation, enhanced mass transfer, and lower pressure drop. In this research, the covalent binding of proteins on to a monolithic matrix was investigated to overcome the drawback of loss and/or denaturing of the biomolecules from physical adsorption and encapsulation method. A chitosan/silica hybrid monolith was prepared and a protein, bovine serum albumin, was covalently immobilized on the column. The prepared monolith was evaluated using the enantioseparation of D,L-tryptophan by CEC. It was found that separation of tryptophan enantiomers with a resolution of 2.44 was achieved by using 20 mmol L−1 phosphate buffer at pH 7.5. A higher chitosan concentration was also proven to be of possible use in the synthesis with the aid of acetic acid as the solvent. The much shorter retention time and increased separation ability demonstrate the advantages of capillary column under investigation.