Fermenters and Yoghurt Making for IGCSE Biology — Transcript

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1. 0:00hello in this video we're thinking about
2. 0:02fermenters and we're thinking about
3. 0:04yogurt making we think about this for a
4. 0:05GCSE biology and specifically these are
5. 0:08paper two topics both of them this is an
6. 0:12image of a fermenter and there are
7. 0:15various parts of it we're going to think
8. 0:16about what those parts do this in here
9. 0:20is the medium of the fermenter and in
10. 0:24here you will have microbes you will
11. 0:26have nutrients in and you'll have air
12. 0:29going in in particular you will need o2
13. 0:31going in in most cases the microbes that
14. 0:35go in here are going to be ones that you
15. 0:36consider particularly valuable you want
16. 0:39to grow lots of them maybe for example
17. 0:41they are transgenic bacteria to make
18. 0:43human insulin that in which case we're
19. 0:45going to be aerobic and we're going to
20. 0:49want to have lots of glucose in here and
21. 0:53we're going to have a little lots of
22. 0:54amino acids in here you're going to need
23. 0:59these and other nutrients besides
24. 1:00because you want glucose for your
25. 1:03bacteria to have fuel for respiration
26. 1:04and you want amino acids so that they
27. 1:06can make proteins and grow but also so
28. 1:09that they can make human insulin itself
29. 1:11that itself is a protein and amino acids
30. 1:13are the building blocks of proteins all
31. 1:16this around here is a fluid is a liquid
32. 1:20suspension and solution of these various
33. 1:23things
34. 1:24now of course microbes themselves don't
35. 1:26dissolve in water and so given the
36. 1:28opportunity they will just settle out to
37. 1:30the bottom down here then that's no good
38. 1:32at all because the ones on the top well
39. 1:35maybe they'd be alright but the ones in
40. 1:37the middle well they wouldn't get any
41. 1:39amino acids or glucose or indeed oxygen
42. 1:41which can be dissolved in this water and
43. 1:43you'll also get a buildup of carbon
44. 1:45dioxide in the middle of those piles so
45. 1:48we don't want settling settling is no
46. 1:52good for us and that's why we have these
47. 1:55paddle stirs here to keep it going
48. 1:57around to keep it well oxygenated and to
49. 2:00stop co2 from building up and to make
50. 2:02sure all microbes get a fair supply of
51. 2:04food
52. 2:05co2 itself will of course be made and so
53. 2:09that co2 will come out here and we have
54. 2:12our gas outlet
55. 2:13to allow that to come out so we've got
56. 2:15Oh to going in we've got co2 coming out
57. 2:18in fact we kind of need to do the gas
58. 2:20exchange for the microbes and this way
59. 2:22how do we know when to do that well we
60. 2:24have these probes they will detect
61. 2:26levels of co2 and of o2 and that will
62. 2:29tell the computer what it needs to do
63. 2:31that's co2 of course is produced by
64. 2:34Arabic respiration aerobic respiration
65. 2:36also generates heat energy now we want
66. 2:44the fermenter to be at a reasonable
67. 2:46temperature in order for the bacterial
68. 2:48enzymes to be working at their optimum
69. 2:52temperature but we don't want it to get
70. 2:54too hot and therefore typically actually
71. 2:56we have cooling water going in this is a
72. 2:59cooling jacket here and it will come out
73. 3:01slightly warmer it will be taking heat
74. 3:04energy away and so therefore it will
75. 3:07cool the fermenter keeping it at an
76. 3:11optimum temperature again as controlled
77. 3:13by the computer we want a tap for the
78. 3:16product and then you'll need to purify
79. 3:20your product later on downstream
80. 3:23processing and there's one little thing
81. 3:25that maybe we've missed out on this
82. 3:26diagram and that would be here that
83. 3:31would be a filter for the air going in
84. 3:35it's going to be really important that
85. 3:38we stop other microbes getting in we
86. 3:41have made in this fermenter a lovely
87. 3:43warm gooey salty sugary amino acid II
88. 3:49oxygenated solution which is perfect for
89. 3:52microbes to grow now of course that's
90. 3:53not just perfect for our transgenic
91. 3:55bacteria to grow as we want them to but
92. 3:57it's also perfect for any other microbe
93. 4:00to grow and so we got to make sure those
94. 4:03things don't get in there so we filter
95. 4:05for the air in and that will keep the
96. 4:08conditions sterile that's really
97. 4:11important and of course beforehand
98. 4:13you're going to want to clean it
99. 4:14properly so that there aren't any
100. 4:16bacteria in there before you start and
101. 4:18you do that with superheated steam now
102. 4:23that's a good reason to use superheated
103. 4:25steam rather than
104. 4:26or something like that which would of
105. 4:28course sterilize it but you don't want
106. 4:30bleach in your product superheated steam
107. 4:32on the other hand will cover every
108. 4:35single surface in that fermenter and
109. 4:37will then just condense out of water
110. 4:40which is perfect it leaves no toxic
111. 4:42residue behind Thank You superheated
112. 4:45steam drives only bacteria are the only
113. 4:48things you might want to grow in a
114. 4:49fermenter there are two other things you
115. 4:51need to think about for GCSE
116. 4:53that is yeast in brewing now that's a
117. 4:55paper one topic we're not going to cover
118. 4:57that in this video but also bacteria for
119. 5:00yogurt making and that we're just about
120. 5:03to have a little look at for both yeast
121. 5:05in brewing and yogurt making for
122. 5:08bacteria we need anaerobic conditions
123. 5:10because we're interested in the product
124. 5:13of anaerobic respiration in those cases
125. 5:15yeast and brewing we want the ethanol
126. 5:18that's made by yeast when they respond
127. 5:21anaerobically that's going to be the
128. 5:22alcohol in fermented drinks such as beer
129. 5:24and in yogurt making we want the lactic
130. 5:27acid made by that bacteria but those
131. 5:29bacteria and we'll have a look at why in
132. 5:32just a moment this is a summary of what
133. 5:36we've just talked about for the
134. 5:38fermenters you may want to pause on this
135. 5:40bit and join it down if that's going to
136. 5:42be useful for you and I'm gonna carry on
137. 5:46here we go yogurt making yogurt this
138. 5:49here is yogurt maker it's pretty simple
139. 5:54you can buy them off an Internet
140. 5:56supplier and in order to make your
141. 5:58yogurt you get UHT milk it's important
142. 6:02that it's UHT I'll talk about that in a
143. 6:04moment and you pour that in and then you
144. 6:06take one spoonful of live culture yogurt
145. 6:11now the live culture yogurt contains
146. 6:16this bacterium here lactobacillus of
147. 6:19Bulgaria's now may contain other
148. 6:21bacteria as well but this is the one
149. 6:22that's specifically mentioned in the
150. 6:23IGCSE syllabus and this bacterium is
151. 6:27still alive in this culture we just need
152. 6:30one spoonful so one spoonful out it
153. 6:33comes thank you and in you go and that
154. 6:37will be enough the bacteria a
155. 6:40waving that spoonful of yogurt will now
156. 6:42be able to feed on this UHT milk and get
157. 6:46all it's lovely proteins and sugars and
158. 6:48fats and themselves reproduce okay why
159. 6:54does this make yogurt well when we
160. 6:57incubate this at 37 degrees C our
161. 7:01lactobacillus bulgaricus their enzymes
162. 7:04will work at optimum temperature and
163. 7:06they will do this conversion they will
164. 7:09take the sugar in milk lactose and they
165. 7:14will convert it into lactic acid fire a
166. 7:18number of steps but essentially we can
167. 7:21just remember it as being by air aerobic
168. 7:23respiration now that's just the same
169. 7:27sort of anaerobic respiration that you
170. 7:29learn about in muscle cells producing
171. 7:32lactic acid that lactic acid will have
172. 7:36the effect of lowering the pH and that
173. 7:40will have two different effects
174. 7:42number one it will preserve the yogurt
175. 7:48for longer now that's because the other
176. 7:54bacteria you might want to come and live
177. 7:55in this yogurt they don't like this
178. 7:57acidic pH and so your yoga will last a
179. 8:01lot longer in the fridge then your milk
180. 8:03will in fact your milk will turn to
181. 8:05something not dissimilar to yogurt if
182. 8:08you leave it there it gets all clumpy
183. 8:09and lumpy and oh no no one likes it no
184. 8:12one like that and it has the other
185. 8:15effect of denaturing the milk proteins
186. 8:25now normally you think about that is a
187. 8:27bad thing but what that actually happens
188. 8:29it causes those soluble milk proteins of
189. 8:31course milk it's just got to contain
190. 8:33protein because it's got a feeder baby
191. 8:35mammal and it's soluble but once you
192. 8:40expose it to acid those proteins
193. 8:43coagulate they solidify now once those
194. 8:49protists coagulate that
195. 8:51thickens the yogurt and that's what
196. 8:59gives you your texture of the yogurt
197. 9:01that you are probably very familiar with
198. 9:03and maybe you love it and maybe like
199. 9:05Mead think it's kind of you know it's
200. 9:08alright it's it's not great it's alright
201. 9:11but there we go and that's how you make
202. 9:12it we mentioned there was a reason that
203. 9:15you use UHT milk
204. 9:16UHT milk has been treated at a really
205. 9:20high temperature an ultra high
206. 9:21temperature that's in order to totally
207. 9:23sterilize it that will give it a much
208. 9:25longer shelf life of course but also
209. 9:27from our point of view the me that we
210. 9:29start off with no other bacteria in our
211. 9:33yogurt maker in our milk and we've got
212. 9:36unfettered access to all those nutrients
213. 9:39for lactobacillus bulgaricus it suffers
214. 9:42no competition from other microbes who
215. 9:44might come along and do things we don't
216. 9:46want them to do to our milk and make our
217. 9:50little horrible
218. 9:51well that's yoga making I hope that's a
219. 9:55helpful video do like and subscribe if
220. 9:57that's the kind of thing you do thank
221. 9:59you