Why is the co-metabolism strategy used in the production of different polyesters in bacteria? O To increase bacterial growth rate O To generate polymers with novel properties O To prevent the accumulation of toxic byproducts O To reduce the cost of the fermentation process
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Co-metabolism refers to the situation where one microorganism uses the metabolic products of another microorganism. Show more…
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Engineering a Fermentation System Fermentation of plant matter to produce ethanol for fuel is one potential method for reducing the use of fossil fuels and thus the $\mathrm{CO}_{2}$ cmissions that lead to global warming. Many microorganisms can break down cellulose then ferment the glucose to ethanol. However, many potential cellulose sources, including agricultural residues and switchgrass, also contain substantial amounts of arabinose, which is not as easily fermented. (EQUATION CANNOT COPY) Escherichia coli is capable of fermenting arabinose to ethanol, but it is not naturally tolerant of high ethanol levels, thus limiting its utility for commercial ethanol production. Another bacterium, Zymomonas mobilis, is naturally tolerant of high levels of ethanol but cannot ferment arabinose. Deanda, Zhang, Eddy, and Picataggio (1996) described their efforts to combine the most useful features of these two organisms by introducing the $E$ coli genes for the arabinose-metabolizing enzymes into $Z$. mobilis. (a) Why is this a simpler strategy than the reverse: engineering $E$. coli to be more ethanol-tolerant? Deanda and colleagues inserted five $E .$ coli genes into the $Z$. mobilis genome: araA , coding for L-arabinose isomerase, which interconverts L-arabinose and L-ribulose; $\operatorname{araB}$, Lribulokinase, which uses ATP to phosphorylate L-ribulose at $\mathrm{C}-5 ;$ araD, L-ribulose 5 phosphate epimerase, which interconverts L-ribulose 5 -phosphate and L-xylulose 5 phosphate; talB, transaldolase; and $t k t A$, transketolase. (b) For each of the three ara enzymes, briefly describe the chemical transformation it catalyzes and, where possible, name an enzyme discussed in this chapter that carries out an analogous reaction. The five $E$. coli genes inserted in $Z$. mobilis allowed the entry of arabinose into the nonoxidative phase of the pentose phosphate pathway (Fig. $14-23$ ), where it was converted to glucose 6 -phosphate and fermented to ethanol. (c) The three ara enzymes eventually converted arabinose into which sugar? (d) The product from part (c) feeds into the pathway shown in Figure $14-23 .$ Combining the five $E .$ coli enzymes listed above with the enzymes of this pathway, describe the overall pathway for the fermentation of six molecules of arabinose to ethanol. (e) What is the stoichiometry of the fermentation of six molecules of arabinose to ethanol and $\mathrm{CO}_{2}$ ? How many ATP molecules would you expect this reaction to generate? (f) Zymomonas mobilis uses a slightly different pathway for ethanol fermentation from the one described in this chapter. As a result, the expected ATP yield is only 1 ATP per molecule of arabinose. Although this is less beneficial for the bacterium, it is better for ethanol production. Why? Another sugar commonly found in plant matter is xylose. (GRAPH CANNOT COPY) (g) What additional enzymes would you need to introduce into the modificd $Z$. mobilis strain described above to enable it to use xylose as well as arabinose to produce ethanol? You don't need to name the enzymes (they may not even exist in the real world); just give the reactions they would need to catalyze.
Q7a. Why mutant fermentation strains needed for industrial process? Put forward your strategy in this regard. Q7b. Do you have strategies that meets the modern-day challenges for the development and microbial production of ̑̑-amylase at industrial scale? [5+5 = 10]
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Engineering a Fermentation System Fermentation of plant matter to produce ethanol for fuel is one potential method for reducing the use of fossil fuels and thus the $\mathrm{CO}_{2}$ emissions that lead to global warming. Many microorganisms can break down cellulose then ferment the glucose to ethanol. However, many potential cellulose sources, including agricultural residues and switchgrass, also contain substantial amounts of arabinose, which is not as easily fermented. Escherichia coli is capable of fermenting arabinose to ethanol, but it is not naturally tolerant of high ethanol levels,thus limiting its utility for commercial ethanol production. Another bacterium, Zymomonas mobilis, is naturally tolerant of high levels of ethanol but cannot ferment arabinose. Deanda, Zhang, Eddy, and Picataggio (1996) described their efforts to combine the most useful features of these two organisms by introducing the $E$. coli genes for the arabinose-metabolizing enzymes into $Z$. mobilis. (a) Why is this a simpler strategy than the reverse: engineering $E .$ coli to be more ethanol-tolerant? Deanda and colleagues inserted five $E$. coli genes into the $Z$. mobilis genome: araA , coding for L-arabinose isomerase, which interconverts $\mathrm{L}$ -arabinose and $\mathrm{L}$ -ribulose; $a r a B$ L-ribulokinase, which uses ATP to phosphorylate L-ribulose at C-5; araD, L-ribulose 5-phosphate epimerase, which interconverts L-ribulose 5 -phosphate and t-xylulose 5 -phosphate $t a l B,$ transaldolase; and $t k t A,$ transketolase. (b) For each of the three ara enzymes, briefly describe the chemical transformation it catalyzes and, where possible, name an enzyme discussed in this chapter that carries out an analogous reaction. The five $E$. coli genes inserted in $Z$. mobilis allowed the entry of arabinose into the nonoxidative phase of the pentose phosphate pathway (Fig. $14-23$ ), where it was converted to glucose 6 -phosphate and fermented to ethanol. (c) The three ara enzymes eventually converted arabinose into which sugar? (d) The product from part (c) feeds into the pathway shown in Figure $14-23 .$ Combining the five $E .$ coli enzymes listed above with the enzymes of this pathway, describe the overall pathway for the fermentation of six molecules of arabinose to ethanol. (e) What is the stoichiometry of the fermentation of six molecules of arabinose to ethanol and $\mathrm{CO}_{2}$ ? How many ATP molecules would you expect this reaction to generate? (f) Zymomonas mobilis uses a slightly different pathway for ethanol fermentation from the one described in this chapter. As a result, the expected ATP yield is only 1 ATP per molecule of arabinose. Although this is less beneficial for the bacterium, it is better for ethanol production. Why? Another sugar commonly found in plant matter is xylose. (g) What additional enzymes would you need to introduce into the modified $Z$. mobilis strain described above to enable it to use xylose as well as arabinose to produce ethanol? You don't need to name the enzymes (they may not even exist in the real world! ; just give the reactions they would need to catalyze.
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