Process Development of Propionic Acid Production by Fermentation Zhong Gu Iowa State University
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Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1997 Process development of propionic acid production by fermentation Zhong Gu Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Chemical Engineering Commons Recommended Citation Gu, Zhong, "Process development of propionic acid production by fermentation " (1997). Retrospective Theses and Dissertations. 11799. https://lib.dr.iastate.edu/rtd/11799 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS This manuscript has been reproduced fiom the microfihn master. 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Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photogr^hs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. UMI A Bell & Howell Informadon ConqsaiQ^ 300 North Zed) Road, Ann Aibor MI 48106-1346 USA 313/761-4700 800/521-0600 Process development of propionic acid production by fermentation by Zhong Gu A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Chemical Engineering Major Professor: Charles E. Glatz Iowa State University Ames, Iowa 1997 DMI Number: 9737713 UMI Microform 9737713 Copyright 1997, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 ii Graduate College Iowa State University This is to certify that the Doctoral dissertation of Zhong Gu has met the dissertation requirements of Iowa State University Signature was redacted for privacy. Major Professor Signature was redacted for privacy. For the Major Program Signature was redacted for privacy. oixme Graduate College iii I dedicate this work to my late father Yongkang. iv TABLE OF CONTENTS ABSTRACT viii INTRODUCTION I Dissertation Organization 1 Literature Review 1 Propionic acid fermentation 1 Acid recovery from fermentation 3 Liquid-liquid extraction with amine 6 The solvent system 6 Extraction chemistry 7 Factors affecting amine extraction 10 Effect of pH 10 Effect of identity of acid 11 Effect of amine concentration 11 Effect of temperature 11 Acid regeneration 12 Solvent toxicity 13 Propionic acid downstream processes 16 PROPIONIC ACID PRODUCTION BY EXTRACTIVE FERMENTATION: PART 1. SOLVENT CONSIDERATIONS 18 Summary 18 Introduction 18 V Materials and Methods 22 Materials 22 Organic chemicals 22 Microorganism and media 22 Methods 23 Partitioning 23 Solvent toxicity 24 Strain screening 24 Single-component solvents 25 Reducing solvent toxicity 26 Distillation 26 Results 27 Partitioning 27 Solvent toxicity 30 Strain screening 30 Smgle-component solvent 33 Reducing solvent toxicity 33 Distillation 39 Discussion 39 Partitioning 39 Solvent toxicity 41 vi Distillation 42 Conclusions 43 Acknowledgments 44 References 44 PROPIONIC ACID PRODUCTION BY EXTRACTIVE FERMENTATION: PART 2. FERMENTATION STUDIES AND ECONOMIC EVALUATION 49 Summary 49 Introduction 50 Materials and Methods 53 Materials 53 Methods 53 Fermentation 53 Economic evaluation 56 Results 62 Fermentation 62 Economic evaluation 67 Discussion 72 Fermentation 72 Economic evaluation 78 Conclusions 79 Acknowledgments 80 References 80 vii EFFECTS OF PROPIONIC ACID ON PROPIONIB ACTERIA FERMENTATION 84 Synopsis 84 Introduction 85 Materials and Methods 88 Materials 88 Microorganism and media 88 Methods 88 Results and Discussion 91 Conclusions 100 Acknowledgments 102 References 102 GENERAL CONCLUSIONS 106 APPENDIX: ESTIMATION OF MASS TRANSFER COEFFICIENTS OF GLUCOSE AND PROPIONIC ACID IN A PACKED BED OF IMMOBILIZED BEADS 110 LITERATURE CITED 112 VIU ABSTRACT The fennentation kinetics of Propionibacterium thoenii strain P20 were studied with calcium alginate bead-immobilized cells without mass transfer limitations. The fermentation was foimd to be significantly affected by the end-product, propionic acid, in the medium. High levels of the acid not only inhibited cell growth, but also changed cell metabolism to produce more byproducts such as acetic, succinic and lactic acids. As a result, substrate consumption rate and propionic acid productivity and yield also decreased. Coupling liquid-liquid extraction of the acid with the fermentation, that is, extractive fermentation, alleviated the inhibitory effects. Solvent selection, based on partitioning and toxicity, was carried out among three solvent systems: Alamine 304-1 in 2-octanol, 1- dodecanol, and Witcohol® 85 NF (oleyl alcohol). For each system, the acid loading per amine molecule decreased with increasing amine concentration; hence, an optimal amine concentration existed. The solvent toxicity to five strains of propionibacteria was determined. Strain P20 was the most solvent-resistant strain and Alamine 304-1 in Witcohol 85 NF was the only nontoxic solvent. Addition of vegetable oils to scavenge the toxic diluents was £dso able to reduce toxicity. Extractive fermentation was carried out with 40% (w/v) bead load of immobilized P20 cells and a hollow-fiber membrane extractor. By maintaining the propionic acid concentration at about 13 g/L, the yields of propionic and acetic acids were more than doubled compared to those of the nonextractive process. Higher acid productivities, an 80% ix reduction of base consumption for pH control, and solvent selectivity of propionic over acetic acid were also achieved. Vacuum distillation produced pxirified acids as the overheads and recyclable solvent as the bottoms. No solvent degradation occurred under the distillation conditions. Based on the experimental findings, economic evaluations of the extractive fermentation process on a 50,000-ton annual production scale were conducted. The process was modified to use whole-cell extraction with a mixer-setder extractor. This process suggested that economic feasibility could only be realized with favorable assumptions such as long-term bead usage, byproduct revenue, and inexpensive substrate. 1 INTRODUCTION Dissertation Organization This dissertation is organized into five parts: the introduction, the three papers submitted to technical journals, and the general conclusions. The manuscripts of the three papers were prepared by the candidate according to the style guides of the journals. The candidate carried out all the work except for the experiments on nonextractive fed-batch fermentation with immobilized cells. Those were conducted by David A. Rickert, an M. S. graduate from the Department of Food Science and Human Nutrition of Iowa State University, and are described in the paper co-authored by Mr. Rickert. An appendix for the third paper is added after the general conclusions, followed by the list of literature cited by the introduction section. Literature Review Propionic acid fermentation Although synthesis of propionic acid by industrial fermentation has been studied since 1923*, production of the acid by fermentation is still not favorable in commercial scale. The drawback results from bacterial metabolism and fermentation kinetics: Propionibacterium species grow slowly ; the end-product is inhibitory to bacterial growth , the highest reported acid concentration reached is about 7% (w/w)'*; byproducts include other acids such as acetic and succinic acids^'^. Downstream processing of such an impure and 2 dilute aqueous solution is difficult. Therefore, the fermentation has to be improved for better end-product tolerance, higher productivity, and less byproduct formation. For better end-product tolerance, studies on bacterial metabolism and strain optimization have been carried out on many microorganisms. The metabolism of propionibacteria was thoroughly reviewed by Hettinga and Reinbold^''. Babuchowski and others^ selected the best propionic acid producer among 90 strains of Propionibacterium. A mutant was also developed with enhanced propionic acid tolerance'. However, the end- product inhibition to cell growth could not be eliminated completely. For higher productivity, various fermentation schemes have been attempted'*''""''*. The key to high productivity was maintaining