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Maximizing Efficient Sugar Consumption Minimizing organic acid production Reducing glycerol production

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Maximizing Efficient Sugar Consumption

Minimizing organic acid production

Reducing glycerol production

Bacteria areSingle-celled organismswhich areProkaryotes whichCan produce infectionAnd undesirable ACIDS and stress to Yeast.

are a fungi which are Eukaryotes Yeast turn sugar into alcohol. Yeast have

many different attributes. Some yeast are better at making alcohol than others

Vinegar (acetic acid) is made from ethanol by the acetic acid bacterium, Acetobacter aceti

Sauerkraut is made by lactic acid bacteria naturally present on cabbage

Pickles are made essentially by the same process for sauerkraut with organisms: Leuconostoc and Pediococcus

Acid is NOT good when Making alcohol

Sources of bacterial contamination

On the feedstock, especially old, wet, or damaged stalks!

On the trucks or from the soil

Bacteria are in the water Well water, open container water, stagnate water Cooling water

Bacteria are in the air Higher in warm and humid environments Summer time they thrive in moist environments

Bacteria are on your person Skin, mouth

sugar → ethanol + carbon dioxide + heat

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Anaerobic respiration with lactic acid formation when invaded by bacteria.

sugar → lactic acid + heat

Certain species of bacteria and wild yeast strains live favorably in ethanol fermentation conditions.

They compete with the yeast and utilize the glucose (simple sugar) and produce stress chemical called glycerol. Both reducing the amount of ethanol that could have been produced. This lowers the ethanol yields and increases undesirable organic acids. Acids kill the yeast

During fermentation, carbohydrates, ethanol, and organic acids are monitored in order to insure that the fermentation process is occurring normally and to insure that undesirable bacteria are kept under control. Also, the mash temperature is kept in a range of 90F to 95F.

Lactic acid: Lactic acid % starts at 0.05 and stays mostly steady when lactic acid bacteria are under control When lactic acid bacteria are present in larger numbers, the lactic acid % in Haiti were extremely high ex: 1.8%

Acetic acid: Acetic acid generally stays in a range of 0.05 to 0.10.

Bacterial cultures:

Bacterial infections can cause large losses in profit

Based on ~1% lactic acid growth at 13 wt% ethanol and $2 gal/ethanol

For example a 250,000 liter ethanol plant infection causes loss of

1% loss = $1,000 per year

4% loss = $4,000 per year

1 organic acid molecule = 1 lost ethanol molecule

1 lactic acid molecule = 1 lost ethanol molecule

Glycerol 2:1 on a weight basis; for every 0.1% w/v glycerol produced, 0.05% w/v ethanol is lost.

Reducing glycerol from a 1.8% to 1.6% w/v theoretically results in 0.1% w/v increase in ethanol.

13.0 → 13.1% w/v increase = ~1,000,000 gal additional EtOH/year

(100,000 MMGY)

800,000 X 16.12% v/v = 128,960 gal EtOH/ferm

800,000 X 16.24% v/v = 129,952 gal EtOH/ferm

~1000 gal EtOH increase per ferm; 3 ferms per day, 360 operating days per year = 1,080,000 gal additional EtOH produced

184/92 = 2 ----- Thus glycerol:ethanol is 2:1 by wt

Yeast stress factors are synergistic; while yeast can tolerate one or two moderate stress factors, several stress factors working together will add infinitely more stress to a yeast culture such as:

pH

Temperature

Ethanol content

Acid and glycerol content

Osmotic pressure

Glucose content

Salt content from water

Glycerol is a waste product produced by “stressed” yeast. It

sends a signal out to stop working because the end is near. This inhibits the yeast from doing their job.

Acid affects the yeast by changing their ideal environment and not allowing them to make alcohol.

Practical ApplicationKeep plant clean and bacteria free

Further Considerations:

Bacteria consuming sugar isn’t the only concern. The negative effects of elevated organic acids are extensive including increased residual sugars, decreased ethanol, increased stress on yeast.

If you have a chronic, recurring infection it may be wise to do some calculations on how much ethanol potential is lost and what capital expenditures could be made to alleviate the source of the issue.

Lactic Acid (produced by heterofermentative LAB) is roughly 1:1 on a weight basis; for every 0.1% w/v lactic acid produced, 0.1% w/v ethanol is lost.

Reducing lactic acid from a 0.4% to 0.2% w/v theoretically results in 0.2% w/v increase in ethanol.

13.0 → 13.2% w/v increase = ~2,000,000 gal additional EtOH/year

(100,000 MMGY)

800,000 X 16.12% v/v = 128,960 gal EtOH/ferm

800,000 X 16.37% v/v = 130,944 gal EtOH/ferm

~2000 gal EtOH increase per ferm; 3 ferms per day, 360 operating days per year = 2,160,000 gal additional EtOH produced

“Reducing lactic acid levels should result in increased ethanol concentration due to glucose consumption via yeast rather than bacteria. Reducing lactic acid from 0.3 to 0.2% w/v

(0.1% w/v difference) theoretically results in a gain of ethanol by 0.05 to 0.1% w/v per fermenter. For a 100-million-gallon/year ethanol plant, this results in a yearly gain of 1–2 million additional gallons ethanol produced per year.”

Phibrochem 2011

Lab technicians test for acids with instruments to save money for the producer

Lactic acid on Hplc

• Lactic acid indicates bacterial contamination

• Primary source is a (LAB) lactic acid bacteria

for every 0.1% w/v lactic acid produced,

0.1% w/v ethanol is lost.

Propagation ? #3

Lactic acid 1.710

Glycerol 2.220

Low glucose

Finished ethanol

Ethanol 99.92

Methanol .0157

DENATURANT type chemicals .065 which does not include the acids and glycerols.

Backwash #1

Lactic acid 2.274

Glycerol 2.770

Backwash #2 Lactic acid 1.806 Glycerol 3.240

Fermentor Lactic acid 1.452 Glycerol 2.832

Backwash What this means:

Dp4 are larger starches Still some glucose left

over Still some ethanol left

over Extremely infected with

Lactic Acid bacteria produce lactic acid out of the glucose

High stress on yeast which are producing glycerol instead of ethanol.

Peak after glucose is probably Fructose or Sucrose which are other sugars that can be fermented.

Backwash What this means: Same as previous

Dp4 are larger starches Still some glucose left over Still some ethanol left over Extremely infected with

Lactic Acid bacteria produce lactic acid out of the glucose

High stress on yeast which are producing glycerol instead of ethanol.

Peak after glucose is probably Fructose or Sucrose which are other sugars that can be fermented.

Fermentor What this means:

Dp4 are larger starches Still some glucose left over Still some ethanol left over Extremely infected with

Lactic Acid bacteria produce lactic acid out of the glucose

High stress on yeast which are producing glycerol instead of ethanol.

Peak after glucose is probably Fructose or Sucrose which are other sugars that can be fermented.

Ethanol production can be higher.

Ethanol production What this means:

Some methanol in product

Other contaminants probably from high acids

Not sure if denaturant had been added

Propagation What this means:

Dp4 are larger starches Still some glucose left over Still some ethanol left over Extremely infected with

Lactic Acid bacteria produce lactic acid out of the glucose

High stress on yeast which are producing glycerol instead of ethanol.

Peak after glucose is probably Fructose or Sucrose which are other sugars that can be fermented.

Ethanol production should be lower in the prop to avoid high glycerol.

Sugar holding well Dirty processing

Sugar trough Resolution

Prop needs cover Fermenters need covers

Stainless steel and pvc piping

Plastic tanks

Ethanol producing yeast

Power washers and sanitation from STS

PVC piping

Washable stainless steel and tanks

Use distillate water to clean with

Washable milling equipment

Better tanks for fermentation

Use briquettes from coconut or bagasse for heat

Heat efficient broilers

Enzyme, nutrient, and STS conditioner, STS yeast trial

Hydrometers, Refractometers and pH meters/paper

New clean buckets and method to clean them

New presses for briquettes

New distillation equipment

Head space improvement to cookstoves

Use of other available waste for feedstock