Using different enzymes in laundry detergents:

[rootone]

Hi!
I am conducting research on possible replacements for the current enzymes used in laundry detergents. Right now, most, if not all detergents use serine protease.
However, cysteine protease is not used in laundry detergents because they oxidize with bleaching agents. I've done quite a bit of research, but I can't figure out why cysteine differs so much from serine, or what cause it to oxidize and not serine.

Moreover, are there ways to prevent the oxidation process of cysteine protease when it mixes with compounds such as Sodium Hypochlorite?

Any information would help! Thanks!

[skuzniewski]

The presence of the thiol group in cysteine causes the oxidation. Cysteine and serine have different chemical structures. Cysteine has sulfur, a -SH group called the thiol. This is absent in the chemical structure of serine. The thiol group in cysteine has high affinity for metals and metals can easily lead to oxidation. Metals are found in water. You can try using an antioxidant to see if it can prevent the oxidation process by the cysteine protease.

[rootone]

Thanks! That was really helpful

If I were to test the oxidation of a compound, would I do this by comparing the mass before and after a reaction?

To carry out this exerpiemnt:
I plan on using pineapple skin pulp (contains cysteine protease) and mix it with sodium hypochlorite and water (and find the mass difference before and after I mixed the solution). Then I will calculate the difference in mass, and compare colour, pH etc.

I will then create a solution made of pineapple pulp and sodium thiosulfate, then mix this solution with sodium hypochlorite and water. I will compare the difference in mass, colour, and pH again in this scenario.

I will then compare the two data sets to determine if the sodium thiosulfate was able to prevent or limit the oxidizing affect of sodium hypochlorite.

Does this sound like a feasible plan that would actually be able to draw results from? Are there other anitoxidants that may break or prevent disulfide bonds in the cysteine protease?

Thank you so much!

[skuzniewski]

Few points to remember:
1. Mass comparison before and after a reaction to find out if oxidation happened or not: You might see a mass change or you might not see a mass change. It all depends on the type of reaction and the reactants involved.

2. Cysteine protease content: Generally, there is more cysteine protease when the fruit is unripe than when it is ripe.

3. Pineapple material: Also, why not try a whole slice of pineapple and crush it? By just using the skin pulp and not the juice, you might have very little cysteine protease to work with.

* My suggestion is to take the data for the weight (remember weight is different than mass, scientifically speaking) before and after, use unripe pineapple, and use a crushed slice or if you want, filter it out using a drainer and work with the juice. My suggestion is to take the weight at time zero (i.e. put the bowl on the scale and put everything in it and record the weight right after you add the last ingredient) and then record the weight again at the final time. Also, I suggest this same point for pH and color change.

4. Variables to consider: You might have to try the experiment at different temperature and amount of water. Think of the detergent with the clothes in the washing machine. There are some detergents designed for cold wash, some for he (less water), and some wash cycles use warm or hot water. Cysteine protease is an enzyme and different enzymes work optimally at different temperature and thus arise the need to do the experiment at different temperature to find the optimal temperature. Also, some enzymes require co-factor(s). Does cysteine protease require a co-factor? If it does, you might have to add in a co-factor. Some of the co-factors are present in water. So you might want to use tap water as that is what the water for the washing machine is. But these metals are present in very low amount in water and might not be enough to make the reaction happen and so you might need to use metals (maybe something like an iron supplement might work). You might want to try pure metals and in different concentrations because a combination of metals or too high of a concentration can inhibit the reaction.

Other antioxidants: There are a whole bunch of them out there. I am sure there are some that can prevent or break disulfide bonds. One place to start will be to look at what products they use for hair perms at a salon. Another place is to look at antioxidants in fruits and pharmaceuticals and research them.

Good luck on the experiment!

[caraskl]

Enzymes present in laundry detergent remove stains. Enzymes are specific for the type of stain they remove, and thus, proteases remove protein-based stain; amylases remove starch-based stains; lipases removed lipid-based stain; and pectinases remove fruit and pectin-based stain. To test the effectiveness of an enzyme as a stain removal, some experiments prepare solutions of enzymes mixed in diluted detergent (http://www.nuffieldfoundation.org/pract ... detergents). In order for an enzyme to work effecively, the pH and temperature conditions must be optimal. For example, amylases and proteases produced by B. Subtilis and B. licheniformis work best in warm alkaline conditions, which are the condititions of most detergent liquid. Moreover, stain-removing enzymes must be effective in the prescense of surface active agents, Mg2+, Ca2+, builders (sodium tripolyphosphate), pefumes, and other additives, because these chemicals are often found in detergent.

In addition, you might want to check out this article for ideas on isolating cysteine protease from pinneapple (http://www.ncbi.nlm.nih.gov/pmc/article ... 7-0239.pdf). Crude pinneapple contains 4 different types of cysteine proteases, 2 of which are found in the stem. These enzymes differ in subtrate specificty and in inhibition profiles. The enzymes were purified using affinity chromatography. When doing your experiment, you might want to differentiate among the activities of the various cysteine proteases in pinneapple, because some enzymes might be more effective as stain removers than others.