(1) Food ingredients by fermentation I araya cloutier

Why is bacterial cellulose 10 times stronger than plant based cellulose?

It has a higher cyrstallinity

What species produce bacterial cellulose?

Acetobacteraceae

Why is bacterial cellulose more crystalline than plant cellulose?

• Due to its ability to create hydrogen bonds with the OH groups.

• More linear than plant cellulose which make it able to have inter and intramolcular interaction in the same polymer chain

Why do bacteria make cellulose?

It makes these when it is in harsh environments.

• It provides structural support and protection.

• It allows the bacterial cells to access nutrients and oxygen from the surrounding medium, facilitating their growth and proliferation

Why can you not make the pore bigger for cellulose production?

The glucan chains willl crystallize intracellularly due to the extra hydrogen bonds which will kill the cell

In alginate, which group can coordinate CA2+ ions resulting in an increase in thinkness?

Guluronic acid groups

can you change mannuronic subunits to glucuronic subunits in alginate?

Yes

What determines the distribution of guluronic acid in the oligomer of alginate?

The processive enzyme or non processive enzyme (less stable)

Why do protein pores in the cell of bacteria that produce alginate have a positive charge?

Alginate is negatively charged, the positively charged amino acids lining the alginate secretion pores in the outer membrane of bacteria attract and guide the negatively charged alginate polymer out of the cell, enabling its export to the extracellular environment

What is the difference between alginate and cellulose biosynthesis?

Alginate is amorphous and cellullose is crystalline. there are more possibilities to modulate the properties of alginate → epimerization / acetylatoin (G→M)

Why are alginates produced by bacteria?

As a survival mechanism

Where is bacterial cellulose synthesized?

From terminal complexes (TC’s)

What do terminal complexes exist of in bacterial cellulose production?

Multiple copies of 4 different subunit of the enzyme benzylsuccinate synthase: BcsA, BcsB, BcsC and BcsD

What does BcsA do in the cellulose biosynthesis?

It is the actual cellulose synthase which uses UDP-glucose as a substrate. It polymerizes glucose units into glucan chains.

What does BcsB do in the cellulose biosynthesis?

It regulates cellulose biosynthesis by binding cyclic diguanylic acid

What does BcsC do in the cellulose biosynthesis?

Its responsible for extrustion and crystallization

What does BcsD do in the cellulose biosynthesis?

It is responsible for extrusion and crystallization and it forms a pore

What two domains does BcsA have?

Binding the donor substrate (UDP-sugar) and binding the acceptor substrate (growing glucan chain)

What coordinates and catalyzes the reaction of chain elongation of cellulose?

Aspartate

What is the rate limiting step in cellulose biosynthesis?

Extrusion and crystallization through BscD

What does the pore that extrudes cellulose consist of?

4 glucan chains of which the N-termini reside inside the pore forming loops

What is the difference between bacterial and seaweed alginate?

• Bacterial alginate can be acetylated

• Bacterial alginate has a higher molecular weight

• Bacterial alginate does not have a GRAS status: Generaly recognized as safe

(In bacterial alginate) On which positions can mannuronic acid be acteylated?

At O2 and O3 position

What enzyme changes mannose-6-phosphate to mannose-1-phosphate?

Phsophomannumutase (AlgC)

What enzyme activates Mannose-1-phosphate to GDP-mannose

GDP-mannose-phyrophosphorylase (AlgA)

What enzyme oxidates GDP-mannose to GDP- mannuronic acid?

GDP-mannose-dehydrogenase (AlgD)

What enzymes polymerize GDP-annuronic acid?

ALg8 & Alg44

What enzymes acetylate GDP-mannuronic acid?

Alg F, I, J, X

What enzymes export GDP-mannuronic acid to form Alginate?

AlgK & AlgE

What enzyme trims the mannose in the periplasm??

AlgL→ lyase

What enzyme convert Manuronic acid to guluronic acid in alginate?

Alg G→ periplasmic C5 epimerase

What is the difference between processive and non-processive epimerases?

• Processive epimerases can give long stretches or blocks of guluronic acid residues while non-processive epimerases introduce G residues in a more random, distributive manner

• Processive epimerases can catalyze multiple reactions while non-processive epimerize in a step by step fashion

What does aspartate do?

It coordinates and catalyzes the reaction of chain elongation of cellulose

What are the main protein characteristics of AlgG?

• It is the epimerase protein

• Processive or non-processive

• Has a charged binding site

What are the main protein characteristics of AlgE?

• It is the export protein

• monomeric

• Charged channel