Tstl Naoufel H S Pta

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Concernant la présentation orale.

Ton oral est parfaite (5:38 mins)

Il y a quelques erreurs, par exemple "the bioplastic", experiences =} experiments, ou "which plastic bags would be the better" =} the best, ou "…in order to look for a reduce reduction in sugar" ou encore "the land become became dry because we didn't hydrated irrigate it correctly"

Attention Ă  la prononciation de certains mots comme "equipment", "based", "compared", "aim", "micro", "purpose",

Il faut bien prononcer les "s" à la 3ème personne du singulier et après chaque mot au pluriel, exemple "the bioplastic that becomes", "which plastic bags"

Attention aussi à la prononciation du morphème –ed : "consumed", "recycled", "faced", "compared", "helped"

Il y a certaines phrases qui restent inachevées ou parfois le son n'est pas terrible car tu as fait des pauses pendant l'enregistrement (surtout vers la fin de ta présentation)!

C'est bien présenté mais il faut publier ton texte sur cette page !



Plastics have invaded our world in fields as diverse in packaging, construction, transport, electrical and electronic equipment, furniture and leisure. Global demand continues to grow. 5,000 billion plastic bags are consumed worldwide each year, or almost 10 million per minute, according to the UN. Only 9% of the nine billion tonnes of plastic the world has ever produced has been recycled. A barely larger share - 12% - has been incinerated. The rest has ended up in oceans, pipes, where it will take thousands of years to decompose completely.
In recent years, rising oil prices have heightened awareness of the limits of fossil resources and the desire for greater climate protection and sustainability. A particular category of this group of materials, namely bioplastics, has aroused interest here.
We are therefore faced with a number of questions that reflect as many hypotheses and imply the problems of our present study:
So how the use of bioplastic bags help to limit environmental pollution?
To answer this question, we carried out eight manipulations . First we proceeded to manufacture a bioplastic film based on corn starch. Then we compared the resistance of the bioplastic , the plastic bags ,and the manufactured. The aim was to see if there is a link between the strength of the plastic and the time of it s degradation. Then we proceeded to composting. The aim was to see how different plastic bags degrade in nature. Then came enzymology, which consists of identifying the bag that degrades in a short time and doing microbiological tests to demonstrate the characteristics of the Bacillus subtilis bacteria and its concentration. Finally, we did the last experiment with Fehling's liqueur in order to look for a reducing sugar.


Experience n°1 : the manufacture of a bioplastic film

In this first experiment, we proceeded to manufacture a bioplastic film based on corn starch. This manipulation will be used to compare the bioplastic bag with the manufactured and plastic bags in order to identify the least polluting bag. To carry out this experiment, we used a list of materials and followed a precise recipe.
The equipment used in this experiment included a pan, a hot plate, a 100 ml beaker, a magnetic rod, a thermometer, a tray, baking paper, 50 ml and 10 ml test tubes, a long pipette, a spatul , glass stirrer,and gloves.
As for the ingredients, we used 5 ml white vinegar, 5 g cornflour, 2 ml glycerol, dye, 45 ml distilled water. The recipe followed consists of the steps described below: we put water in the pan to be heated to prepare the water bath. In the beaker of 100 ml, we put 45 ml of distiled water and 5 ml of white vinegar. Then we put the beaker in the pan in the water bath with the thermometer until the temperature of the liquid reaches 100°c. Then we added about 2 ml of glycerol and stirred the mixture. After that we weighed 5 g of maize starch which we added as a rain, always stirring the mixture, then we added 2 drops of the dye, collected the beaker in the water bath with the gloves and poured the hot liquid into a sheet of baking paper in the tray. After that we spread the mixture with the glass stirrer and let it dry for a week. Finally we removed the film gently from the mould.

Experience n° 2: the resistance of plastic

Is there a link between the resistance of the plastic and it’s degradation time?
To answer this question, we used masses from 1 to 200 kg, a dynamometer and three different plastic bags (the biodegradable, the plastic bag , and the manufactured)
this experiment was complicated and was to realised, a correct distance between the holes ensure that the plastic bag would not be destroyed. We had to rely on the biodegradable plastic bag , it was the first one to be destroyed. Also, the normal plastic bag and manufactured plastic bag have a high resistance. We had to place it in the vacuum with our hands underneath in case it breaks because otherwise the mass would touch the table.

Experience n°3 : composting

The purpose of this experiment was to see if when we put a plastic bag in nature and see its degradation. As certain bag, it is possible to put it in the compost (biodegradable bag the one of fruits and vegetables in the supermarket: Oseo). So we made 16 different composts, 8 indoors at room temperature and 8 others outdoors with the bad weather (winter temperature). In this experiment we used the Bacillus subtilis bacterium to be able to see if with or without it changes some things to the plastic when it would be in nature. We left the compost for a month. At the end of this term we took back the ones that were outside and we had no difficulties, the winter temperatures with its bad weather was enough to feed the composts with what they needed to have a good compost. While for the indoor one there were some complications. One week after making the compost with or without the bacteria. Even with or without plastic, we had to put back at least 10mL of water twice a week to moisten the soil because it dried out very quickly when it was at room temperature. With these difficulties we managed to get usable results.

Experience n°4 : land degradation with different bags

The aim of the protocol is to find out whether pollution can have harmful effects on the land. Plastic pollution is caused by the accumulation of plastic in the environment. We want to know how the land reacts to different plastic bags? For this we have made a protocol comparing two different types of the land (autoclaved land and the land ) with three types of plastics (plastic, biodegradable, and manufactured), we will also use the bacteria Bacillus subtilis. The protocol will allow to see the effects of the different pieces of plastic on the land with or without Bacillus subtilis.
Flow chart of the handling:
After incubation, the land containing the plastic bag does not change and becomes dry in the presence and absence of Bacillus subtilis bacteria. For the autoclaved land that containing the plastic bag is placed over the mold without the bacteria and becomes dry with the bacteria. Then the land containing the biodegradable bag does not change but becomes dry in the presence and absence of the Bacillus subtilis bacteria. The autoclaved land that contains the biodegradable bag becomes mud with the bacteria and becomes dry without the bacteria. Finally, the land that contains the manufactured plastic bag does not change in the presence and absence of the bacteria. The autoclaved soil containing the manufactured bag also does not change its appearance in the presence and absence of the bacteria.

Experience n°5: enzymology

The purpose of enzymology is to allow us to know which plastic bag is degraded in a minimal amount of time. To have a degradation of the different bags, we use alpha amylase, an enzyme that destroys the plastic particles and Bacillus subtilis which contains the enzyme. In this experiment we divised the work in two parts . For our first test of this manipulation, we couldn't even read the results because we had made a big mistake by having a volume in each tube that wasn't equal everywhere so the results were false. Then in the second test, the volumes were all equal to 2mL, the results were correct but some of them were negative so we made the decision to repeat the manipulation a third time to check if we had made a mistake or not. Once we did it again we had results that were all positive or equal to 0 absorbance. After the reading, we had to transform the absorbance into concentration at the beginning we tried several ways to get a result in concentration using the kit, but we had a lot of trouble understanding it. Then when we found the right formula we understood why this experiment was useful for our subject.
We know from the kit that the concentration of the standard is high, it means that there is glucose that was produced during this experiment and more precisely 100mg/dl. We also used a blank with distilled water to have a final concentration equal to 0.000mg/dL. Then we continue to read the results.

Experience n°6 : Microbiological test of Bacillus subtilis bacteria

This protocol allows us to determine the different characteristics of the Bacillus subtilis bacterium. To do this we did differents manipulations: First we inoculated the bacterium in different solutions such as Hugh and Leifson, VF agar, GTS and starch agar using a bacterial suspension. We took with an öse in slant agar which contains the Bacillus subtilis bacterium, then we inoculated it into a hemolyse tube containing about 1mL of distilled water. These microbiology experiments will allow us to see how the Bacillus subtilis bacterium grows, its route of attack, its appearance but especially to see if it degrades the starch. Because plastic contains starch. Does Bacillus subtilis hydrolyse starch? Will the Bacillus subtilis bacterium make it easier to degrade the plastic?
-Hugh and Leifson: allows us to determine the attack of glucose used as an energy source for most bacteria, it is studied to the presence of glucose as the only carbohydrate but also bromothymol blue as a pH indicator. We were able to observe in the tube, that it had changed colour to green at the bottom and yellow at the top of the tube. We can say that there is an attack on glucose in the presence of oxygen, so it is an oxidative .
-VF agar: allows to determine the respiratory type of a bacterium. We observe a culture on the surface of the VF tube, there is the presence of oxygen. It is therefore a strict aerobic.
GTS Agar: is a basic medium that allows the culture of non-demanding bacteria of the strain. We have observed large colonies with irregular contours and flat, opaque consistency, yellow pigmentation, so it is a pure strain.
-Starch agar: allows the search for starch hydrolysis by amylase. After incubation, diode contained in Lugol is added to the starch agar to reveal the presence or absence of starch around the colonies. We can observe clear halos around the culture. The starch degrades and the bacterium possesses amylase, that is to say the enzyme. To conclude it is a starch plus.

Experience n°7 : mass concentration of bacillus subtilis bacteria

The protocol allows us to calculate the mass concentration of Bacillus subtilis bacteria. To find the concentration, we performed three absorbances with a control and two tests.
We were able to calculate the concentration using the following formula:

Experience n°8 : fehling's liqueur

The aim of the protocol is to search for the reducing sugar, (glucose). For this we know that when a plastic is in contact with Bacillus subtilis or alpha amylase, glucose is formed. Reducing sugars are considered as simple sugars that give electrons in a redox reaction. This is why Fehling's liqueur will contain blue copper II ions. When it is hot the precipitate turns brick red in the presence of reducers. Is there reducing sugar in the test solution ? glucose, fructose and maltose? They have a fonction. In this first experiment we mixed 0.5 mL of Fehling solution ( Fehling A + Fehling B) with 1 mL of test solution, which in this case was alpha amylase. Then we cut a small piece of a plastic bag and put it back into the tube and finally put the tube in a water bath at 90°C.


1/ The result is a coloured film that can be used for handling and to form a plastic bag made from.
2/ We notice that the plastic bag and the manufactured plastic bag have the same resistance. Whereas the biodegradable plastic bag has a lower resistance than the plastic bag and the manufactured plastic bag. We can therefore conclude that there is no link with degradation, the most environmentally friendly, is the manufactured plastic. Whereas the plastic bag that takes the longest time to degrade is the plastic bag that is the most deplorable for the environment.
3/ For indoor composts no drying of the compost was observed. The plastic bag made with or without the Bacillus subtilis bacteria began to destroy itself, the manufactured plastic became in small pieces, then for the biodegradable bag with the Bacillus subtilis bacteria, it did not change whereas without the bacteria it folded up on itself. For the normal plastic bag whether it is inside or outside it does not change. Then the plastic made outside with or without the bacteria, it has decomposed. But there are still small pieces left and finally the biodegradable plastic does not change no matter where it is. It can be concluded that for the normal plastic bag it takes longer to degrade. Then the biodegradable plastic bag, it also takes more time but less than normal plastic. To finish the manufactured plastic bag, it would have taken only a few more days for it to degrade completely and therefore it is the one that takes the least time to degrade.
4/ For the land protocol we had difficulties, at first because of the supports because we took test tubes. They prevented us from seing the land and the piece of plastic properly. Then we optimised for petri dishes as a support. This allowed us to see the land but also the piece of plastic correctly. But unfortunately the land was dry because of the incubation temperature. We were able to get about correct results. This is why we observe after incubation that the land becomes very dry. In the presence or absence of Bacillus subtilis with the piece of plastic bag, biodegradable and manufactured. Then the autoclaved land containing the plastic bag is placed over the mould without the bacteria and becomes dry with the bacteria. The autoclaved land containing the biodegradable bag becomes dry without the bacteria. The autoclaved land that contains the biodegradable bag and the manufactured piece of bag becomes dry with and without the bacteria.
To conclude, knowing that the plastic bag is the most harmful to the environment, the two different types of land were observed. We were able to conclude that autoclaved land reacts the most to plastics.

5/ when the concentration is highter , the plastics will be degraded faster. In this case Bacillus subtilis (contains alpha amylase) is more effective than alpha amylase against the plastic. The non degradable plastic bag has a concentration of 0.000 mg/mL so we can say that it has not degraded even after 50 minutes. We can also observe that the manufactured bag is the one in both cases where the concentration is high in a short time. We can conclude that the bag that degrades the fastest is the manufactured bag.
6/ To conclude the Bacillus subtilis bacterium is a pure strain, it degrades glucose, there is an attack on glucose only in the presence of oxygen, so it is an oxidative pathway. We have observed a culture only in the presence of O2, its respiratory type is therefore strictly aerobic. Finally we obtain a starch + agar because we observed clear halots around the culture after the addition of Lugol this indicates a hydrolysis of the starch.
7/ We calculated the mass concentration of Bacillus subtilis bacteria and obtained 1.2 CFU/ml.
8/ For the Fehling protocol we first obtained a blue tube, there is no presence of reducing sugar. It can be concluded that the solution to be tested does not contain reducing sugars. In a second step we used distilled water and 8 drops of glucose in a tube; we obtained a red precipitate, there is presence of reducing sugars. (. It would have taken more time, precisely to see the total degradation of the manufactured plastic bag).



In view of the results of the various experiments carried out, we can therefore answer the following question: « way would the use of bioplastic bags make it possible to limit environmental pollution »? The best plastic bag to reduce pollution is the manufactured plastic bag because it is the one that degrades the fastest. This is proven in the composting protocol, with the bag that is in pieces and of a different colour. Once we have used it, if we leave it in nature, in contact with land. It will degrade, about 2 months, compared to the normal plastic bag where the duration is at least 400 years. But we also know that not everyone can make their own homemade plastic bag, because some people don't have the materials and don't have the means. The alternative is to take the biodegradable plastic bag, which limits environmental pollution because we have proved that it destroys more slowly than the manufactured one, but faster than normal plastic. Also in contact with a source of high heat, it deforms and begins to destroy itself. So a bioplastic bag would limit pollution because it is the second one that takes the least time to degrade, it will result in limiting environmental pollution.

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