sugarcane1 sts
TRANSCRIPT
Maximizing Efficient Sugar Consumption
Minimizing organic acid production
Reducing glycerol production
Bacteria
Yeast
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
____________________________________________
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 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
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.
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