Industrial Biotechnology Flashcards
At ScotBio, what organism do they use to produce blue food colouring
derived from Spirulina, a cyanobacteria
What is extracted from Spirulina and how?
the light-harvesting protein, phycocyanin is extracted and purified using photobioreactors
After purification, what happens to the protein
is formulated into powder & sold to distributers and manufacturers
how is cultivation of spirulina achieved
using open or closed systems, where the organism is grown to produce biomass or primary/secondary metabolites
Open system designs
raceway ponds
open ponds
tanks
advantages of open systems (2)
- low cost
- low energy requirement for culture mixing
disadvantages of open systems (3)
- large areas must be scaled up for optimal growth (main cost associated with land)
- contamination risks (weather conditions like wind may blow soil particles, chemicals e.g. pesticides, or algal grazers)
- productivities are seasonal (in summer higher levels of sunlight, more growth)
Closed system designs
bioreactors & photobioreactors
- tubular reactors
- flat plate reactors
- air-lift reactors
Why are closed systems more suitable for culturing cyanobacteria (3)
- allow for better control over environmental conditions required for growth (temp, light & nutrient level)
- minimises risk of contamination (contained in sterile, sealed environment)
- more efficient for space utilisation and resource consumption
At ScotBio, what do they use
Patented LED technology to provide optimal light levels required for Spirulina growth
disadvantages of closed systems (6)
- bio-fouling (accumulation organic matter surfaces, affecting performance)
- regular cleaning & maintenance necessary (issue if tank with corners, hard to CIP)
- foaming (excess gas, foam reduces SA for gas exchange & light pene)
- overheating due to lights or LEDs
- growth of benthic algae (build up of DO, limit growth)
- very high capital costs (design & installation - specialised equipment & monitoring)
Types of culture
batch
fed-batch
continuous
what is a batch culture
microorganisms are grown in a closed system with a fixed amount of nutrients, allowing them to consume this until depleted
what is a fed-batch culture
- additional nutrients periodically added into the system
- sustains growth over a longer time
- allows for more control over nutrient level, optimising growth
what is a continuous culture
new nutrients are added while an equal amount of culture medium is removed (allows for constant growth of organisms, maintaining steady-state condition)
what are the main processes in downstream processing (7)
harvesting
lysis/extraction
separation
concentration
purification
formulation
drying
what is harvesting
the recovery of biomass from the culture, or removal of culture, leaving cells in reaction vessel
what is harvesting based on
- filtration (using sieves, filter sheets or membrane filtration)
- gravity-based (using separators like centrifuges or decanters)
- sedimentation tanks
why is lysis required and what do we need to consider
to release intracellular target metabolites into the extractant
must consider thickness and composition of cell wall
lysis methods
- mechanical (agitation, high-pressure homogenisation)
- chemical/biological (acid/alkali, enzymatic, solvent extraction)
- physical/electromagnetic (free/thaw, ultrasound-assisted, microwave-assisted extraction)
why must we consider the polarity/hydrophobicity of target compounds during lysis/extraction
if proteins are water soluble we must use an aqueous extraction buffer, so proteins can be solubilised and easier to extract
why must we consider the stability of target compounds during lysis/extraction
if pigments are heat or pH-sensitive, proteins produced will be prone to denaturation if extraction process too vigorous
what is separation for
- to separate the complex mixture of molecules, cell debris and suspended solids left over from extraction
- makes it easier to purify later
- we may want to fractionate compounds into different product lines
what are some gravity-based separation techniques (4)
- separators (centrifuges & decanters)
- sedimentation tanks
- flocculants (aid removal of larger debris)
- encourage precipitation of certain chemical groups
how can distillation be used in the separation stage
- can utilise differences in boiling points to separate liquids and volatiles from other liquids
- freeze distillation can also be used to separate components (good for heat unstable compounds)
different types of chromatography for separation (3)
- reverse-phase
- normal -phase
- HILIC size-exclusive
chromatography for separation
- widely used technique to separate compounds
- many different types & can be scaled
- based on different compounds interacting with the stationary phase
- or based on size
why is concentration necessary
target compounds are often in very low concentrations, so we must make them amenable to processing, drying and shipping
concentration techniques (3)
crossflow filtration
chromatography
evaporation
what does the level of purification depend on
- final application of product
- legislation
final applications for the product
- technical grade - industrial use
- laboratory grade - for use in teaching labs
- food grade - for use in foods
- reagent/BP/USP grade - for use in food, drug, body laboratory, & medical purposes
- ACS grade - highest purity level, for use as analytical standards
purification techniques
- diafiltration
- chromatography
- sterile/microfiltration
diafiltration
- utilise ultrafiltration & nanofiltration membranes
- removes salts & low MW molecules
- repeatedly diluting & concentrating
- increases the purity of retained molecules
chromatography (for purification)
- can bind (adsorb) compound to solid station phase
- other compounds remain in mobile phase & pass through column
- can then unbind analytes in another mobile phase
- this concentrates and purifies them
sterile/microfiltration
- removes contaminating microbes and particulate matter
- passes through filter with small pores
- depth filtration (type of microfiltration) is commonly used to clarify liquids by removing certain contaminants
purification
- anti-solvent precipitation
- salting out
- isoelectric precipitation
why do we often need to formulate the extract, concentrated & purified compound with excipients
- improves functionality
- improves bioavailability
- increases stability & shelf-life
- improves organoleptic qualities (smell, colour, taste)
strategies for formulation
- simply mixing excipients
- homogenising mixtures to create micelles, emulsions or double emulsions
- add gelling agents to create gels
- formulate & dry compounds to micro-encapsulate them
what is dried
- whole biomass
- cell extracts
- purified compounds
why are these compounds dried
- increase shelf-life
- aid micro encapsulation
- help supply-chain logistics for transport
what does drying choice depend on
- heat stability of compounds
- technoeconomics
- other technical considerations
methods for drying
- drum drying
- vacuum drying
- spray drying
- fluid bed drying
- lyophilisation (freeze drying)
drum drying
- cheap
- great for low value commodities
- may damage heat sensitive compounds
vacuum drying
- economical
- lower residence time than drum drying
spray drying
- allows fine control over final moisture content and particle size
- very short exposure to high temperatures
lyophilisation (freeze drying)
- useful for very heat-sensitive compounds
- expensive
- slow
- products need freezing beforehand
