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Bài giảng Kỹ thuật phản ứng sinh học: Chương 4 Thiết kế bể phản ứng theo mẻ, bể phản ứng theo mẻ có bổ sung cơ chất, bể phản ứng liên tục, cung cấp cho người học những kiến thức như: Các dạng thiết bị phản ứng sinh học; Các thông số trong các thiết bị phản ứng; Quy trình thiết kế bể phản ứng sinh học; Đánh giá hệ thống bể phản ứng sinh học. Mời các bạn cùng tham khảo!
http://buihongquan.com Chương Thiết kế bể phản ứng theo mẻ, bể phản ứng theo mẻ có bổ sung chất, bể phản ứng liên tục 4.1 Khá i niệ m bả n 4.2 Cá c dạ ng thiế t bị phả n ứng sinh họ c 4.3 Cá c thong só cá c thiế t bị phả n ứng 4.4 Quy trình thiế t kế bể phả n ứng sinh họ c 4.5 Đá nh giá hệ thó ng bể phả n ứng sinh họ c 12/23/2018 Bioreaction engineering 169 http://buihongquan.com http://buihongquan.com Bioreactor Design Bioreactors have requirements that add complexity compared to simpler chemical reactors Usually three-phase (cells, water, air) Need sterile operation Often need heat removal at ambient conditions But biological reaction systems have many advantages Some products can only be made by biological routes Large molecules such as proteins can be made Selectivity for desired product can be very high Products are often very valuable (e.g Active Pharmaceutical Ingredients: APIs) Selective conversion of biomass to chemicals Well established for food and beverage processes 12/23/2018 Bioreaction engineering 171 http://buihongquan.com Bioreactor Design Enzyme catalysis Cell growth and metabolism Cleaning and sterilization Stirred tank fermenter design Other bioreactors 12/23/2018 Bioreaction engineering 172 http://buihongquan.com Enzyme catalysis Enzymes are biocatalysts and can sometimes be isolated from host cells Low cost enzymes are used once through: amylase, ligninase High cost enzymes are immobilized for re-use Enzymes are usually proteins Most are thermally unstable and lose structure above ~60ºC Usually active only in water, often over restricted range of pH, ionic strength Enzyme kinetics: Michaelis-Menten equation: C R C 12/23/2018 R = reaction rate C = substrate concentration α, β = constants Bioreaction engineering 173 http://buihongquan.com Enzyme Catalysis: Immobilization Feed Reactor Filter Enzymes can sometimes be adsorbed onto a solid or encapsulated in a gel without losing structure They can then be used in a conventional fixed-bed reactor If the enzyme is larger than the product molecule, it can be contained in the reactor using ultrafiltration or nanofiltration M Product 12/23/2018 Bioreaction engineering 174 http://buihongquan.com Bioreactor Design Enzyme catalysis Cell growth and metabolism Cleaning and sterilization Stirred tank fermenter design Other bioreactors 12/23/2018 Bioreaction engineering 175 http://buihongquan.com Cell Growth Cell growth rate can be limited by many factors Availability of primary substrate Typically glucose, fructose, sucrose or other carbohydrate Availability of other metabolites Vitamins, minerals, hormones, enzyme cofactors Availability of oxygen Hence mass transfer properties of reaction system Inhibition or poisoning by products or byproducts E.g butanol fermentation typically limited to a few % due to toxicity High temperature caused by inadequate heat removal Hence heat transfer properties of reaction system All of these factors are exacerbated at higher cell concentrations 12/23/2018 Bioreaction engineering 176 http://buihongquan.com Cell Growth and Product Formation in Batch Fermentation II III IV Live cell concentration I V Cell growth goes through several phases during a batch Innoculation: slow growth while cells adapt to new environment II Exponential growth: growth rate proportional to cell mass III Slow growth as substrate or other factors begin to limit rate IV Stationary phase: cell growth rate and death rate are equal V Decline phase: cells die or sporulate, often caused by product build-up Intracellular product concentration I Batch time 12/23/2018 Bioreaction engineering 177 http://buihongquan.com Cell Growth and Product Formation in Batch Fermentation II III IV V Intracellular product Live cell concentration I Intracellular product concentration accumulation is slow at first (not many cells) Product accumulation continues even after live cell count falls (dead cells still contain product) 12/23/2018 Batch time Bioreaction engineering 178 http://buihongquan.com Exercise: Where Should We Operate? II III IV Intracellular product concentration Live cell concentration I V Extracellular product, continuous process If the product can be recovered continuously or cells can be recycled then we can maintain highest productivity by operating in Phase IV Batch time 12/23/2018 Bioreaction engineering 183 http://buihongquan.com Bioreactor Design Enzyme catalysis Cell growth and metabolism Cleaning and sterilization Stirred tank fermenter design Other bioreactors 12/23/2018 Bioreaction engineering 184 Cleaning and Sterilization http://buihongquan.com Biological processes must maintain sterile (aseptic) operation: Prevent infection of desired organism with invasive species Prevent invasion of natural strains that interbreed with desired organism and cause loss of desired strain properties Prevent contamination of product with byproducts formed by invasive species Prevent competition for substrate between desired organism and invasive species Ensure quality and safety of food and pharmaceutical grade products Design must allow for cleaning and sterilization between batches or runs Production plants are usually designed for cleaning in place (CIP) and sterilization in place (SIP) Continuous or fed-batch plants must have sterile feeds Applies to all feeds that could support life forms, particularly growth media Including air: use high efficiency particulate air (HEPA) filters 12/23/2018 Bioreaction engineering 185 http://buihongquan.com Design for Cleaning and Sterilization Reactors and tanks are fitted with special spray nozzles for cleaning See www.Bete.com for examples Minimize dead-legs, branches, crevices and other hardto-clean areas Minimize process fluid exposure to shaft seals on pumps, valves, instruments, etc to prevent contaminant ingress Operate under pressure to prevent air leakage in (unless biohazard is high) 12/23/2018 Bioreaction engineering 186 http://buihongquan.com Cleaning Policy Typically multiple steps to cleaning cycle: Wash with high-pressure water jets Drain Wash with alkaline cleaning solution (typically 1M NaOH) Drain Rinse with tap water Drain Wash with acidic cleaning solution (typically 1M phosphoric or nitric acid) Drain Rinse with tap water Drain Rinse with deionized water Drain Each wash step will be timed to ensure vessel is filled well above normal fill line 12/23/2018 Bioreaction engineering 187 http://buihongquan.com Sterilization Policy Sterilization is also a reaction process: cell death is typically a 0th or 1st order process, but since we require a high likelihood that all cells are killed, it is usually treated probabilistically Typical treatments: 15 at 120ºC or at 135ºC SIP is usually carried out by feeding LP steam and holding for prescribed time During cool-down only sterile air should be admitted Feed sterilization can be challenging for thermally sensitive feeds such as vitamins – need to provide some additional feed to allow for degradation 12/23/2018 Bioreaction engineering 188 http://buihongquan.com Continuous Feed Sterilization Steam Mixer Holding coil Feed To vacuum Expansion valve Flash cooler Sterile product Holding coil must have sufficient residence time at high temperature Expansion valve shaft is potential contamination source 12/23/2018 Bioreaction engineering 189 http://buihongquan.com Heat Exchange Feed Sterilization Coolant Feed Holding coil Sterile product Condensate Steam Uses less hot and cold utility Possibility of feed to product contamination in exchanger Mainly used in robust fermentations, e.g brewing 12/23/2018 Bioreaction engineering 190 http://buihongquan.com Bioreactor Design Enzyme catalysis Cell growth and metabolism Cleaning and sterilization Stirred tank fermenter design Other bioreactors 12/23/2018 Bioreaction engineering 191 http://buihongquan.com Stirred Tank Fermenter Most common reactor for biological reactions Can be used in batch or continuous mode Available from pressure vessel manufacturers in standard sizes Vessel size (m3) 0.5 Vessel size (gal) 150 1.0 300 1.5 400 800 7.5 1500 2000 15 4000 25 7000 30 8000 Typically 316L stainless steel, but other metals are available Relatively easy to scale up from lab scale fermenters during process development: high familiarity 12/23/2018 Bioreaction engineering 192 http://buihongquan.com Typical Stirred TankAgitator Fermenter drive Growth medium feed Air M Coolant out Coolant in Foam breaker Steam in (during sterilization) Cooling coil Baffle Agitator blade Sparger Condensate out Product out 12/23/2018 Bioreaction engineering 193 http://buihongquan.com Design of Stirred Tank Fermenters Decide operation mode: batch or continuous Estimate productivity (probably experimentally) Even in continuous mode, several reactors may be needed to allow for periodic cleaning and re-innoculation Establish cell concentration, substrate feed rate, product formation rate per unit volume per unit time Hence determine number of standard reactors to achieve desired production rate: assume vessel is 2/3 full Determine run length: batch time or average length of continuous run Determine mass transfer rate and confirm adequate aeration (see Ch15 for correlations) Determine heat transfer rate and confirm adequate cooling (see Ch19 for correlations) Determine times for draining, CIP, SIP, cool down, refilling Recalculate productivity allowing for non-operational time (CIP, SIP, etc.): revisit step if necessary 12/23/2018 Bioreaction engineering 194 http://buihongquan.com Bioreactor Design Enzyme catalysis Cell growth and metabolism Cleaning and sterilization Stirred tank fermenter design Other bioreactors 12/23/2018 Bioreaction engineering 195 Shaftless Bioreactors http://buihongquan.com • Use gas flow to provide agitation of liquid • Eliminates pump shaft seal as potential source of contamination • Design requires careful attention to hydraulics Off gas to vapor recovery Gas feed Liquid feed Off gas to vapor recovery Liquid feed Gas feed Draft tube Sparger Liquid product Liquid product Gas loop reactor 12/23/2018 Baffle tube reactor Bioreaction engineering 196 http://buihongquan.com Example: UOP/Paques Thiopaq Reactor Biological desulfurization of gases with oxidative regeneration of bugs using air Reactor at AMOC in Al Iskandriyah has six 2m diameter downcomers inside shell 12/23/2018 Bioreaction engineering 197 ... fixed-bed reactor If the enzyme is larger than the product molecule, it can be contained in the reactor using ultrafiltration or nanofiltration M Product 12/23/2018 Bioreaction engineering 1 74. .. concentration of cells, g/l t = time, s μg = growth rate, s-1 Cell growth rate usually has similar dependence on substrate concentration to Michaelis-Menten equation: s = concentration of substrate,... special spray nozzles for cleaning See www.Bete.com for examples Minimize dead-legs, branches, crevices and other hardto-clean areas Minimize process fluid exposure to shaft seals on pumps, valves,