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
