Bioprocess and Fermentation

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Bioprocess and Fermentation
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Industrial Bioprocesses

• Better consumer acceptance
• Agricultural and industrial waste management
• Conversion efficiency
• Economic values
• Energy
• Raw materials
• End products
• Facility

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Microbial proteins as a food and feed

• Yeasts contribute to about 5 total protein
  content in white bread
• High lysine content of yeast protein
• Protein source
• By 1914, about 10,000 tons of dried yeast
  available as feed
• Acute protein shortage in World War II stimulated
  the industrial production of yeasts, usually
  Candida utilis from wood hydrolysates and sulfite
  waste liquor
• Converting agricultural or industrial waste to
  utilizable foods

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Biomass

• Traditional substrates
• Sugars or starchy materials can be hydrolyzed by
  enzymes
• Cane molasses, starchy grains, wood sugar (Wood
  hydrolysates, sulfite waste liquor), whey
• Common microbes
• Saccharomyces cerevisiae, S. uvarum, Candida
  utilis, Kluyveromyces fragilis

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Substrates and Nutrition Requirements

• Carbon, N, phosphorus, minerals, vitamins
• Vary among microbes

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Single cell protein (SCP)

• Microbial cells can contain up to 40-65 proteins
• SCP Protein or protein concentrates extracted
  from microbial cells
• Yeast cells nucleotides account for 10-15 of
  total N

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Economics

• Process capital intensive
• Raw material 45-75
• Energy 12-37
• Labor 5-11
• Depreciation 6-10
• Uncertainty
• Substrate availability at the location

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Nutritional Value of Microbial Biomass

• As components of food or feed, mainly contribute
  to protein nutrition
• Protein content highest in bacteria and lowest in
  the filamentous fungi
• For feed, the high nucleic acid content is OK
• Human do not possess urate oxidase, accumulation
  of uric acid can cause gout

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Use in foods

• Inactivated dry yeasts often included in
  fabricated foods such as baked goods, baby foods,
  soups, gravies, meat extenders, etc.
• Up to 2
• Desirable flavor
• Activated cells sold in healthy food industry as
  tablets or dry powders (often fortified with
  water soluble vitamins)
• Yeast autolysate (yeast extract)
• 5nucleotides-flavor enhancer
• 5-inosinic acid, 5-guanylic acid
• Made from nucleosides (RNA isolated from biomass
  of C. utilis) by phosphohydrolase

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Use in feeds

• A major fraction of brewers yeast and C. utilis
  produced is used in feeds in US
• Active dry yeasts or compressed yeasts used to
  inoculate cereal grain mash, incubate and dried,
  as feed supplement
• Relieve short of proteins for feeding monogastric
  animals and ruminants
• Pet food industry a major outet
• Small conc. in dog, cat foods and fish, bird foods

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Fermentation Alcohol as a Fuel Source

• Energy alternative
• Technical feasibility
• Main pactician
• US
• Assume annual use of 110 billion gal of gasoline,
  10 blend will need 11 billion gal of ethanol
• If corn used as raw material, need 4-4.5 billion
  bu, about 70 of the US production
• Government indirect tax incentive 40cents/gal
  ethanl
• Brazil
• Extensive effort
• Target 80/20 blend
• Extensive government support

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Raw Materials

• Generally 100 lb fermentable sugar (as glucose)
  yield about 40-50 lb of ethanol (6-7.5 gal)
• Starchy materials similar yield based on the dry
  weight of carbohydrate
• Complete hydrolysis of 100 lb of starch yield
  about 110 lb of glucose, but mostly 90
  conversion
• Cellulosic raw materials substantially lower

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Sugar-containing Raw Materials

• Any sugar-containing fruits and juices
• By-product molasses
• Contain 50-55 fermentable sugar
• Basis of the production of rum
• High osmotic pressure protects from microbial
  spoilage, easily transportable
• Juice of sugar beets or sugar cane
• Developing countries produce about 11 million
  tons more sugar in the 1985 than 1975, can be
  convert to 1.6 billion gal of ethanol

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Sugar-containing Raw Materials

• Cheese whey contain 6 solids, 3/4 lactose
• Practical and economical
• But impact small
• US 35 billion lb of cheese whey available from
  the production of 3.5 billion lb of cheese
• Generate 100 million gal of ethanol annually

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Starchy Raw Materials

• Cereal grains (rice, wheat, corn), root crops
  (cassava, yam), or tubers (potatoes)
• US corn is the most abundant source of starch
• Mashing of corn
• Barley malt
• Brewing use high level of malt
• Distilling industry only 10 of malt
• Industrial alcohol production use bacterial and
  fungal amylases instead of barley malt, more
  efficient

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Microorganisms

• Saccharomycess cerevisiae (dough, ale and
  distilled beverage yeast)
• S. uvarum (lager beer yeast)
• C. utilis also ferment pentoses
• Microbial growth and ethanol production inhibited
  by high conc. of ethanol
• Productivity decrease when alcohol conc above
  5-7 (batch fermentation can reach 10-13 alcohol)

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Fermentation Nutrients

• In some instances supply of certain nutrients may
  be limited
• Yeast need the following for growth of 100 lb of
  yeast solids
• 7-8 lb of nitrogen from N source (ammonia,
  ammonium salt, urea, aa)
• 2.5lb P (as P2O5)
• Minor quantity of potassium, magnesium, calcium
  salts and trace minerals
• Vitamin rare but thiamin often accelerates
  fermentation
• S. cerevisiae required biotin

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Fermentation

• Batch Fermentation
• No need for pure culture condition
• Total fermentation time between 48-72 hrs
• Final alcohol conc of 6-8 by vol
• Proteinaceous residue valuable feed product
• About 25.5 kg corn yields 2.3-2.6 gal ethanol and
  7.7 kg of distillers dried grains
• Alternative process wet milling process
• glucose syrup, 15-30 hrs
• Continuous Fermentation
• Cell Recycle maintain high yeast cell
  population without, cell number declines
• Aeration
• Vacuum Fermentation

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Additional Aspects

• Distillation
• Energy
• Economics
• Commercial plants