OFFICIAL39 According to the speakers, why is cellulose such a significant potential source of energy?

[00:00.00]NARRATOR: Listen to part of a lecture in a biology class.
[00:03.60]FEMALE PROFESSOR: Your reading for today's class was about potential alternative sources of energy. [00:08.67]So one thing I want to do today is consider one of those potential energy sources, cellulose.
[00:15.31]Who can tell us what cellulose is? Allen?
[00:19.89]MALE STUDENT: Cellulose, yeah, it's a tough organic molecule… made of simple sugars. [00:24.70]It's found in the walls of all plant cells… in grass, trees… all plants, [00:29.87]and, well… there's more cellulose than any other organic molecule on Earth.
[00:34.90]FEMALE PROFESSOR: Good. It's also a potential tremendous source of energy, in part because there's so much of it.
[00:41.69]Now, many organisms live on the energy they derive from consuming cellulose—like many species of bacteria… or cows and goats. [00:50.90]Cows and goats have evolved highly specialized digestive systems that allow them to metabolize cellulose.
[00:57.52]MALE STUDENT: But it's hard for most species to process cellulose?
[01:00.59]FEMALE PROFESSOR: Yes, and it's been very hard to develop a controlled way to process cellulose in a lab, so that we can use the energy that's stored in it. [01:09.13]It needs to be converted into ethanol.
[01:12.05]Let me explain…. [01:13.56]Ethanol is a liquid, a kind of alcohol that is derived from processing sugars from plants, often corn, [01:20.61]and it can be used as fuel. [01:22.70]Many researchers believe it is the key to ending the reliance on gasoline.
[01:27.72]The problem is that the amount of energy we get from corn-based ethanol isn't much more than the amount of energy that gets put into making it, [01:36.55]so it's not really worth it. Tina?
[01:39.68]FEMALE STUDENT: But ethanol made from cellulose is different?
[01:44.13]FEMALE PROFESSOR: Yes—it's possible to get a vastly better energy yield on cellulose-based, or cellulosic, ethanol.
[01:51.83]FEMALE STUDENT: OK, so why don't we just use cellulosic ethanol?
[01:56.09]FEMALE PROFESSOR: Well, the problem is that the current method for processing cellulose into ethanol is very expensive and can't be done on a large scale.
[02:04.87]See, currently, there are two key steps in the process.
[02:09.21]The first is breaking the cellulose down into sugars. [02:12.91]This is done with an enzyme, a specific type of protein. [02:17.13] And second, after the enzyme has broken down the cellulose, yeast and other microorganisms—microbes—are added to ferment those sugars into cellulosic ethanol.
[02:28.42]Thing is, though, we're not too good at producing the enzymes that break down cellulose. [02:34.42]Those proteins are very difficult to make, to just assemble in a lab, [02:38.82]so usually we extract enzymes from microorganisms that produce them naturally. [02:44.36]Unfortunately, this is slow, expensive, and just not very efficient
[02:49.92]MALE STUDENT: So are they trying to develop a better way to make enzymes?
[02:53.87]FEMALE PROFESSOR: Actually, there's a company that thinks they can do better than that. [02:57.49]It'd be more efficient, and therefore cheaper, to combine the two steps I mentioned into one. [03:03.22]That is, have a single organism that breaks down cellulose and then produces ethanol. [03:09.11]So, what this company is doing is searching around the world and gathering naturally occurring microorganisms that do both things.
[03:17.07]I mean, the best key to unlocking the power of cellulose may well lie in a rare species of bacteria or yeast in a jungle somewhere.
[03:25.47]So, researchers at this company have discovered some microorganisms that process cellulose and produce ethanol. [03:32.55]Now, they’re working on enhancing, improving, certain natural characteristics of these microorganisms… manipulating them with sophisticated technology… to make them work even more efficiently. [03:44.97]The goal, which seems to definitely be within reach, is to design and engineer a superbug, a specific kind of microbe, that makes cheap, commercial production of cellulosic ethanol a real possibility.