Effect of temperature on the enzyme pectinase in fruit juice production.

Authors Avatar

Effect of temperature on the enzyme pectinase in fruit juice production

AIM: To investigate the effect of temperature on the work of the enzyme pectinase in fruit juice production.

INTRODUCTION

        It is stated that temperature has an effect on Enzymes. I am going to investigate this fact using my chosen enzyme Pectinase. This enzyme is used in the fruit juice industry and I am going to use this enzyme to explore the question: How Does Temperature Affect Enzymes?

BACKGROUND INFORMATION

        Enzymes are biological catalysts that speed up the rate of a reaction without being changed or used up in any way. They   are protein molecules that are tailored to recognize and bind specific reactants and speed their conversion into products. These proteins are responsible for increasing the rates of all of the many thousand of reaction taking place inside cells.

        Activation energy is the energy barrier over which the molecules in a system must be raised for a reaction to take place. The use of enzymes lowers the activation energy so the reaction can proceed at a faster rate.

           

( GRAPH TAKEN FROM REFERENCE 7)

                A number of factors affect the activity of enzymes in speeding conversion of reactants to products. These factors are;

1.  PH: Each enzyme has an optimal pH range that help maintain its normal configuration in an environment which it operates. The tertiary structure of a protein depends on interactions such as hydrogen bonding, between R groups. A change in pH can alter the ionization of these side chains and disrupt the normal configuration and in some case denature the enzyme. A denatured protein can not combine with a substrate.

2. SUBSTRATE CONCENTRATION: At very low substrate concentration, collisions between enzyme and substrate molecules are less frequent and the reaction proceeds slowly. As the substrate concentration increases, there reaction rate initially increases proportionately as collisions between enzyme molecules and reactants become more frequent   until further increases in substrate concentration have no effect on there reaction rate. At this point the enzyme is saturated and the reaction remains at the saturation level.

3. TEMPERATURE:  More information on this particular factor is going to be presented a little later.

                Pectin is a molecule which has a structure similar to starch, the only difference is that the repeating unit of pectin is galacturonic acid instead of glucose as in starch. Galacturonic acid has a similar structure to glucose apart from the fact that one of the carbons has a carboxylic acid group (-COOH) attached to it. Pectin is found naturally in fruits, where its function is to help hold plant cell walls together, they are bound together by calcium ions (Calcium Pectate)  and are important components of the first layers of a cell wall to be laid down, which is known as the middle lamella.

                         

(Picture taken from Reference  7  )

                Pectin is found naturally in fruits, where it has the important function of helping to hold plant cell walls together. As a fruit ripens, the plant produces proteolytic enzymes which convert the insoluble protopectin of the fruit to more soluble forms, causing the fruit to soften. When fruits are mashed and pressed to form juices, making it cloudy and causing the colour and flavour to deteriorate.  They also increase the viscosity of the juice, making it difficult to obtain optimal yields. For fruit manufacturers, the addition of industrial Pectinase between mashing and pressing causes complete de-pectination so that a good quality, clear juice is obtained which retains its stability when concentrated.

                (Picture taken from Reference 1   )

                Pectinase is the name of the enzyme used industrially in obtaining juice from a fruit. It works by breaking down pectin between fruit cells which ‘unglues’ them so they can slip past each other, therefore releasing the fruit juice. Pectin forms gels that bind liquid and this is the reason why Pectinase improves juice extraction. Pectinase works by splitting the bonds between the galacturonic acids to shorten the pectin chain. They are widely used in the fruit juice industry to help extract fruit juices. They also have the additional task to help clarify and modify fruit juices.

                Industrially, Pectinase is made using the micro-organism ERWINIA CAROTOVORA, a soft-rot bacterium. This is a valuable source of Pectinase because the micro-organism is easy to manipulate genetically and the result is a high yield of pectinase which can be easily extracted. For these purposes, it is easiest and cheapest to extract the enzymes from bacteria which can be grown on a huge scale.

Join now!

HOW IS PECTINASE MADE INDUSTRIALLY?

                  This is done using Biotechnology; the micro organism is first grown in bulk in a fermenter, which is a large vessel in which the micro organisms are grown. Pectinase is made using batch fermentation and is secreted from the cells as an extra cellular enzyme, which can be purified more easily. The advantage of Pectinase compared with some other enzymes is the fact that it can be used after purification with no need to be immobilised.

PICTURE OF A FERMENTER (Picture taken from Reference  7  )

Microbes are preferred ...

This is a preview of the whole essay

Here's what a teacher thought of this essay

Avatar

*** A mostly well researched and carried out experiment that has produced some usable data. The candidate does need to ensure that terms like accuracy, precision, reliability or validity are correctly used at A level. To improve: Research and rationale The rationale for the experiment is discussed and justified in terms of its scope and appropriate biological principles are discussed. A reasonable number of sources that were not standard A level text were quoted. The background could have been extended to include more on the different ways in which pectinase is used to increase fruit juice production. For example pulp can be left to oxidize for some time to rid the pulp of enzyme inhibitors. Planning There could be more consideration given to the key variables in the experiment as a number of key variables were omitted in the discussion. It is often better to list these in a table, with their appropriate control measures and an explanation given as to the likely effect on the experiment if these are not controlled well. The inclusion of controls to the experiment would have made the consideration of the results much easier. The prediction could be made quantitative and greater biological knowledge used to explain it. The attempts to assess safety are superficial and would gain little credit under most current guidelines. Observation The candidate seems to have carried out the experiment well and recorded sufficient data. The headings of the table should include all units. Statistical tests were used appropriately to analyse the data. Analysis and Evaluation The choice of graph illustrated the trend well and the use of ICT included correctly plotted points, not a smooth curve. The explanations were sound and related to basic biological knowledge. The candidate should have considered the controls in the experiment more carefully as their lack meant that some of the interpretations of enzyme stability were dubious. The anomalies were recognized and commented upon. The modifications to the experimental methodology that were suggested were a little limited in nature and could have been mor thoroughly explored but there were sensible extensions proposed.