Systems, compositions, and methods of fermentation with
Methods, compositions, and systems for propagation and fermentation, particularly large scale operations for production of ethanol and dried distiller's grain are provided. Addition of Z. mobilis to propagation and/or fermentation decreases lactic acid bacterial contamination.
1 . A method of fermentation comprising:
(a) grinding grain to form a ground grain;
(b) adding water to the ground grain to form an aqueous slurry;
(c) contacting the slurry with a yeast;
(d) contacting the slurry with a Z. mobilis prior to step (c) or simultaneously with step (c);
(e) maintaining the slurry under growth conditions over time; and
(f) recovering one or more products of fermentation;
wherein the one or more products of fermentation comprise reduced glycerol relative to products generated in a fermentation with the yeast in the absence of Z. mobilis ; or
wherein residual starch after fermentation is lower relative to residual starch after fermentation with the Z. mobilis in the absence of yeast.
2 . The method of claim 1 , wherein the ground grain or slurry is bacterially contaminated.
3 . The method of claim 1 , wherein the fermentation is performed in the absence of one or more antibiotics.
4 . The method of claim 1 , wherein a product of fermentation is fermentation solids.
5 . The method of claim 1 , wherein a product of fermentation is ethanol.
6 . The method of claim 5 , wherein step (f) further comprises separating ethanol from fermentation solids.
7 . The method of claim 1 , wherein the growth conditions comprise a temperature of at least about 30.0 degrees Celsius.
8 . The method of claim 2 , wherein the bacterial contamination is lactic acid bacterial contamination.
9 . The method of claim 2 , wherein the bacterial contamination is reduced compared to a similar fermentation performed in the absence of Z. mobilis.
10 . The method of claim 1 , wherein the Z. mobilis exhibits an early growth rate exceeding that of the added yeast.
11 . The method of claim 10 , wherein during fermentation (i) ethanol concentration rises, (ii) Z. mobilis ethanol production rate decreases to a rate less than yeast ethanol production rate after (i), and (iii) the concentration of ethanol continues to rise after (ii).
12 . The method of claim 2 , wherein the Z. mobilis growth inhibits growth of the contaminating bacterium.
13 . The method of claim 12 , wherein ethanol produced initially by the Z. mobilis inhibits growth of the contaminating bacterium.
14 . The method of claim 1 , wherein the Z. mobilis exhibits an initial ethanol production rate that exceeds that of the added yeast.
15 . The method of claim 1 , wherein the grain is bacterially contaminated at any one of steps (a), (b), (c), (d), or (e).
16 . A method of fermentation comprising:
(a) grinding grain to form a ground grain;
(b) adding water to the ground grain to form an aqueous slurry;
(c) contacting the slurry with a yeast;
(d) contacting the slurry with a Z. mobilis;
(e) maintaining the slurry under growth conditions over time; and
(f) recovering one or more products of fermentation;
wherein during fermentation (i) ethanol concentration rises, (ii) Z. mobilis ethanol production rate decreases to a rate less than yeast ethanol production rate after (i), and (iii) the concentration of ethanol continues to rise after (ii);
wherein the one or more products of fermentation comprise reduced glycerol relative to products generated in a fermentation with the yeast in the absence of Z. mobilis ; or
wherein residual starch after fermentation is lower relative to residual starch after fermentation with the Z. mobilis in the absence of yeast.
17 . The method of claim 16 , wherein the ground grain or slurry is bacterially contaminated.
18 . The method of claim 16 , wherein the fermentation is performed in the absence of one or more antibiotics.
19 . The method of claim 16 , wherein a product of fermentation is fermentation solids.
20 . The method of claim 16 , wherein a product of fermentation is ethanol.
21 . The method of claim 16 , wherein step (f) further comprises separating ethanol from fermentation solids.
22 . The method of claim 12 , wherein levan produced by the Z. mobilis inhibits growth of the contaminating bacterium.
23 . The method of claim 12 , wherein acetic acid produced initially by the Z. mobilis inhibits growth of the contaminating bacterium.