Preparation of Lactate from the fermentation of cabbage Essay Example

Preparation of Lactate from the fermentation of cabbage Essay Equipment and Materials:* 300g of finely shredded cabbage* 300 cmà ¯Ã‚ ¿Ã‚ ½ 3% w/v sodium chloride solution* Small metal weights* Burette containing 0.1 M sodium hydroxide solution* Phenolphthalein indicator solution and pipette.* Elastic bands* Hoffman clip* Large paper bag* A pair of scissors* Temperature probe* pH probe* 15 cmà ¯Ã‚ ¿Ã‚ ½ bent glass pipette with 3 cm rubber tubing* Beaker* Adhesive tape.Method:300 g of finely shredded cabbage and sodium chloride was placed in 1 dmà ¯Ã‚ ¿Ã‚ ½ beaker. Three slices of plastic bags with three small holes were cut for the pH probe, the temperature probe and a pipette. The plastic cover was placed over the surface of the cabbage. The probes were inserted through the holes cut and were made as airtight as possible with adhesive tape. A rubber band was placed around the beaker and pressed down with two weights to prevent as much air as possible. The initial pH and temperature were recorded daily for 6 days. Samples of the acid produced (Lactate) were taken for the calculation of the acid content.Diagram:Results and Calculations:Sampling of acid content 5cmà ¯Ã‚ ¿Ã‚ ½ of the acid was removed using a pipette and was added to distilled water in a beaker. This mixture was titrated against 0.1 M of sodium hydroxide using 2 drops phenolphthalein as the indicator since we are titrating a strong base against a weak acid. Results obtained from the titration are shown below:Result tableRough (cmà ¯Ã‚ ¿Ã‚ ½)1st reading (cmà ¯Ã‚ ¿Ã‚ ½)2nd reading (cmà ¯Ã‚ ¿Ã‚ ½)Final burette reading8.1014.2019.70Initial burette reading2.458.5014.20Volume of base (NaOH) used5.655.705.50Average titre volume = 5.65 + 5.70 + 5.503= 5.62 cmà ¯Ã‚ ¿Ã‚ ½% Lactic acid = titre volume, cmà ¯Ã‚ ¿Ã‚ ½ x molarity of NaOH x mol. mass of Lactatecmà ¯Ã‚ ¿Ã‚ ½ sample x 10Titre volume = 5.62 cmà ¯Ã‚ ¿Ã‚ ½Molarity of NaOH = 0.1 Mcmà ¯Ã‚ ¿Ã‚ ½ sample = 5cmà ¯Ã‚ ¿Ã‚ ½Molar mass of lactate =molecular formula CH3CHOHCOOH (2-Hydroxypropanoic acid)= (12 x 3) + (1 x 6) + (16 x 3)= 36 + 6 + 48= 90g/mol% Lactic acid = 5.62cmà ¯Ã‚ ¿Ã‚ ½ x 0.1M x 90 g/mol50= 1.0116= 1.01 %.Evaluation:The aim of this experiment was to produce lactic acid and find the acid content produced. This involved fermenting finely shredded pieces of cabbage in salt solution under anaerobic conditions then titrating the product gained against sodium hydroxide so as to find the percentage yield of lactate.It was observed from the graph obtained that the pH decreases as the days went by and it was also noticed that the temperature increased to about 28à ¯Ã‚ ¿Ã‚ ½C during the process as high temperatures favour the growth of the bacteria. These results gain provide sufficient evidence to prove that we actually produce lactic acid i.e we met our purpose (or objective) of the whole experiment which was producing lactate.Comparing both percentage yield calculated and the true value which is 2.27%, I can conclude that the results used in the titration process was fairly accurate because the range between the two values is not very much(1.26) The lower value( 1.01%) got may have been due to different reasons, some of which are explained below:The presence of different bacteria in the bioreactor as we did not cultivate Lactobaccilus Plantarum the bacterium responsible for the production of lactate. There must have been different bacteria in there and must have probably hindered the bacteria from producing sufficient product which obviously led to the low yield i.e different reactions were probably occurring at the same time as the production of lactate and so led to different products being produced and the low yield of lactate.The low yield derived might have been due to the presence of low pH-due to lactate (product from the fermentation). From the results derived from the computers we could see that as the days went by, the volume of lactic acid increased thereby decreasing the pH and it is a well known fact that Lactobacillus Plantarum (as well as other bacteria and enzymes) cannot work in an acidic environment because they have a pH near 7 so this must have prevented Lactobacillus Plantarum from producing more lactic acid as it activity and effects were hindered by the increase in the concentration of lactate.The fermentation set up was left for only six days which is quite a short time when compared to how long it should have been left for which is about 2 weeks (minimum). This gave the reaction conditions and the organism involved a very short time to work on the cabbage fully to get as much product as possible i.e this prevented the bacteria from producing sufficient amount of lactate in a shorter period of time.The fermentation set up might not have been subjected to the right temperature as it was left at room temperature for six days and we did not know exactly the appropriate temperature for the reaction conditions until the end of the fermentation process when we got the results from the computer with the use of t he probe.There might not have been sufficient cabbage to ferment to get enough products or the cabbage used may have not have had enough nutrients or may have been decayed and not have been fresh. All thesecould have been due to abnormalities of the cabbage and would obviously have led to a lower yield since the sugar content (glucose) was not sufficient to obtain a completely fermented product since the bacteria Lactobacillus Plantarum requires a source of nutrients for metabolism because the energy requirements of micro-organisms are very high.In the handout we used for the fermentation process, we were asked to remove the product (lactate) aseptically. I read up the meaning and found out that it meant the fermenter should have no contamination whatsoever i.e the air around the bioreactor must be sterilised and the equipment should also be cleaned with hot water before use and also the culture medium should be sterilised in the fermenter by passing steam through it.I noticed that we did not carry out any of these suggestions above and this may also have led to the low yield since the process was probably contaminated and might have resulted in other compounds being produced.Also, the low yield produced might have been due to errors incurred during the titration process done by different sets of people. For example the apparatus used i.e the pipette, conical flask and all other apparatus might not have been clean. The meniscus on both the pipette and the burette may have been read inaccurately and too many drops of phenolphthalein indicator may have been used. This would have resulted in us getting the wrong titre volume which would lead to a wrong percentage yield of lactate since only 2 or 3 drops were meant to be used.However in future, to obtain a purer product and an increase in the accuracy of my results and the yield of my product, I would:* Ensure that Lactobacillus Plantarum (one of the important bacteria involved in the conversion of sugars to lacti c acid) is first cultured alone and then added to the mixture containing the cabbage leaves and sodium chloride solution in clean apparatus and environment. This would avoid other products from being produced along with lactate thereby decreasing its yield and purity since there would be no other bacteria to produce other products. Also we could add more Lactobacillus Plantarum and remove the used up one at regular intervals to ensure sufficient product.* Increase the temperature of the internal and external surroundings of the bioreactor where the fermentation is taking place because we can confirm from the results shown on the graph that a higher temperature favours the reaction conditions. And using the results obtained from the probe and the computer we can see that the internal temperature rose to 28?C during the reaction process and then reduced after the process thereby reducing the pH which indicated that lactic acid was being produced this shows that the bacteria are formul ated to produce lactate at extremely high temperatures at reduced pH levels. So this indicates that increasing the temperature would obviously enable the bacteria to produce more lactic acid as temperatures above 22à ¯Ã‚ ¿Ã‚ ½C favour the growth of lactobacillus species.* Ensure that I use much more older cabbage because it is said that they have more sugar (nutrients) in them and therefore produce better lactic acid with a higher yield. Also I would use very very fine and thinly shredded cabbage so as to ensure a maximum surface area for the bacteria to work on which would lead to an increase in the production of lactic acid.* Ensure that the reaction process is left for a longer period of time as this would give the bacteria sufficient time to convert the sugar (glucose) present in the cabbage to lactic acid thereby leading to an increase in the yield of the product.* Increase the salt content in which the cabbage would be soaked a little bit (even if adding too much salt may inh ibit the bacteria but add to the firm ness of the cabbage) since the salt causes an osmotic imbalance which results in the release of water and nutrients from the cabbage leaves. The fluid expelled is an excellent growth medium for the micro-organisms (Lactobacilli Plantarum) involved in the fermentation. Secondly, the salt concentration used inhibits the growth of many spoilage organisms and pathogens . Although increasing the salt content too much might inhibit the micro-organism, it is best to increase it a bit to a moderate level to obtain a higher yield.* I would ensure that throughout the fermentation oxygen be excluded because the presence of oxygen would permit the growth of some spoilage organisms, particularly the acid-loving molds and yeast since the reaction taking place is an anaerobic reaction and has to be carried out in the absence of oxygen.Glucose pyruvate lactic acid + CO2 + 2 ATP* I would also ensure that I do more than enough repeat readings when titrating so th at I can be sure that the average result is really accurate since taking averages reduces random errors incurred during the experiment.In future, instead of using the apparatus we used which consisted of a beaker, elastic bands, large plastic bag to cover etc, I would use the apparatus which consists of a conical flask with a rubber bung as the cover with holes in it so that the probes could be inserted in them because after the experiment it was noticed that the product was smelling. This is because the micro-organism involved in the fermentation find oxygen toxic and do not grow well in its presence. Also, oxygen is prevented because the growth of the spoilage bacteria which will make the product smell is favoured by oxygen.This method is better because less air gets into it unlike the other method we used which enabled oxygen to enter it as the plastic bag was not very effective in its supposed function and made the product smell. In the new method, oxygen would be excluded as mu ch as possible to ensure that anaerobic conditions predominate. If the fermentation becomes too aerobic (i.e with oxygen), a strong offensive odour will be noticed and this will reduce the yield of Lactate.