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    Delivering Bifidobacterium
    By Robert H Olley | January 8th 2013 11:00 AM | 8 comments | Print | E-mail | Track Comments
    About Robert H

    Until recently, I worked in the Polymer Physics Group of the Physics Department at the University of Reading.

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    Some years ago, I was a bit mystified as to the distinction between prebiotics and probiotics. 

    These days, one can easily look them up on Wikipedia, and find that prebiotics are meant to encourage the growth of ‘good’ bacteria in the gut, while probiotics are supposed to deliver the bacteria directly. 

    Prebiotics are generally soluble oligo- or polysaccharides, known as dietary ‘fibre’, and one of the best sources of these is chicory root


     
     

    Chicory root and flower

    The history of probiotics starts back in the 19th century with the work of Ilya Ilyich Mechnikov, who received the 1908 Nobel Prize in Physiology or Medicine  for his discovery of phagocytes, along with Paul Ehrlich (treatment of syphilis).  Mechnikov’s theory, that certain white blood cells could engulf and destroy harmful bodies such as bacteria, met with scepticism from leading specialists including Louis Pasteur, Emil Adolf von Behring and others. At the time most bacteriologists believed that white blood cells ingested pathogens and then spread them further through the body.
     
    Mechnikov also developed a theory that aging is caused by toxic bacteria in the gut and that lactic acid could prolong life. Based on this theory, he drank sour milk every day. His book The Prolongation of Life: Optimistic Studies, along with his studies into the potential life-lengthening properties of lactic acid bacteria, inspired Japanese scientist Minoru Shirota to begin investigating the causal relationship between bacteria and good intestinal health, eventually leading to the development of a bacterial strain Lactobacillus casei strain shirota which from 1935 is the basis of Yakult (ヤクルト the Japanese name based on ‘yoghurt’: 养乐 or 益力多 ‘benefit happiness/strength a lot’, depending on where you are in China.)
     
    But — the big question — do the ‘good’ bacteria actually reach the gut?  In order to reach the intestine, where they are needed, they have to pass the stomach with its very acidic gastric juice.  Microencapsulation is widely used these days for delivering drugs (and lots of other things) so why not bacteria?  There has been, much work on this, reviewed in The Gut Microbiota and Human Health with an Emphasis on the Use of Microencapsulated Bacterial Cells [1], which includes a Table of types of microcapsules available for the targeted delivery of probiotic bacteria.

    Three references there are given to complex capsules made of the two polymers alginate and chitosan, however there is some more recent research into developing multilayer systems.  Again, the two main polymers are the same, namely Alginate, derived from seaweed, and Chitosan, derived from crustacean shells.



    Alginate

    Chitosan


    Although these are both polysaccharides, they have significantly different properties which allow them to work better in harmony when passing through the stomach.  Alginate is in general a very good encapsulator, but it does not protect the microbes sufficiently from gastric juice.  Chitosan, at first sight, seems to labour under two disadvantages.  It is a known antimicrobial agent and is yet is degraded by microbial action, especially by the enzyme chitosanase.  (Paradox?  Maybe one is the solid form, the other in solution).  However, if the inner layer of the capsule is alginate, chitosan is very slow to diffuse in to the microbes, while chitosan ionically bound to the alginate is attacked much more slowly by the enzyme.

    In Layer-by-layer coating of alginate matrices with chitosan–alginate for the improved survival and targeted delivery of probiotic bacteria after oral administration, the problem is attacked by building a multilayer fortress around the bacteria.  The model probiotic, Bifidobacterium breve, were encapsulated into an alginate matrix before coating in multilayers of alternating alginate and chitosan.  Bacteria encapsulated in different numbers of multilayers were treated, and it was found that three layers of chitosan-alginate gave the greatest survival.  Of just over 1000,000,000 microbes* per millitre, more than half survived after being soaked in model gastric fluid for the requisite time (typically 2 hours), whereas unencapsulated bacteria were reduced to less than 1000 per ml.

    * strictly speaking, colony-forming units (CFU).

    Bifidobacterium breve is commonly offered as a probiotic supplement.  The Wikipedia article deals with the whole Bifidobacterium genus as a whole, but searching for B. breve yields many results from people marketing probiotic products, and as sources of information they might be biased, and generically overlooking the problem of travel through the stomach.  I doubt, though, if we will see encapsulated bugs in ‘foodie’ products any day soon.  But where someone has a clinical condition involving imbalance of the intestinal microflora, this might turn out to be a useful method of delivery.

    So does this mean that there is no point in consuming Yakult?  That would depend on how directly the bacteria were exposed to stomach fluid.  The advice from one of the authors is that the bacteria are most vulnerable when the stomach is empty and the pH is low.  So if you like Yakult, take it with meals.


    [1] Journal of Biomedicine and Biotechnology; Volume 2011 (2011), Article ID 981214, 12 pages; doi:10.1155/2011/981214
    Review Article: The Gut Microbiota and Human Health with an Emphasis on the Use of Microencapsulated Bacterial Cells by Satya Prakash, Catherine Tomaro-Duchesneau, Shyamali Saha, and Arielle Cantor

    [2] Journal of Materials Chemistry B, 2013, 1, 52: DOI: 10.1039/c2tb00126h
    Layer-by-layer coating of alginate matrices with chitosan–alginate for the improved survival and targeted delivery of probiotic bacteria after oral administration
    Michael T. Cook, George Tzortzis, Vitaliy V. Khutoryanskiy and Dimitris Charalampopoulos

    Comments

    Bonny Bonobo alias Brat
    Mechnikov also developed a theory that aging is caused by toxic bacteria in the gut and that lactic acid could prolong life. Based on this theory, he drank sour milk every day. His book The Prolongation of Life: Optimistic Studies, along with his studies into the potential life-lengthening properties of lactic acid bacteria, inspired Japanese scientist Minoru Shirota to begin investigating the causal relationship between bacteria and good intestinal health, eventually leading to the development of a bacterial strain Lactobacillus caseistrain shirota which from 1935 is the basis of Yakult 
    'Mechnikov died in 1916 in Paris from heart failure'. Whoops, maybe he overlooked a few other important aspects of health and longevity? Interesting article Robert :)
    My latest forum article 'Australian Researchers Discover Potential Blue Green Algae Cause & Treatment of Motor Neuron Disease (MND)&(ALS)' Parkinsons's and Alzheimer's can be found at http://www.science20.com/forums/medicine
    UvaE
    Prebiotics are generally soluble oligo- or polysaccharides, known as dietary ‘fibre’, and one of the best sources of these is chicory root
    Chicory roots are about 8% inulin(fiber). The source also reports that when roasted, inulin converts to oxymethylfurfural, which is at least partly responsible for the coffee-like smell.
    It's an old nomenclature that neither I nor chemspider recognize. In any case in regular coffee, furfurals are not responsible for any of the typical aromas. But I digress...!

    Bonny Bonobo alias Brat
    In any case in regular coffee, furfurals are not responsible in any of the typical aromas. But I digress...!
    Interesting digression though Enrico, trying to understand what is responsible for coffee's typical aromas and why doesn't it taste as good as it smells?i The article you linked to says that :-
    Coffee aroma is responsible for all coffee flavor attributes other than the mouthfeel and sweet, salt, bitter, and sour taste attributes that are perceived by the tongue. Therefore, it might be said that coffee aroma is the most important attribute to specialty coffee. Even instant coffee has the components responsible for stimulation of our taste buds. The difference, however, is that instant coffee lacks most of the aromatic volatile compounds causing a dramatic decrease in the overall coffee flavor....Coffee aroma is perceived by two different mechanisms. It can either be sensed nasally via smelling the coffee through the nose or retronasally. Retronasal perception occurs when the coffee is either present in the mouth or has been swallowed and aromatic volatile compounds drift upward into the nasal passage...
    ...The number of aromatic compounds found in coffee increases every year. Today the number is well over 800, and as our analytical methods become more precise, more will be uncovered. Yet, the perception of coffee aroma is dependent upon both the concentration of the compound and its odor threshold. With that said, understanding coffee aroma is not as difficult as understanding how over 800 coffee elements interact with the olfactory epithelium.
    Recently resuming working full time again has one big drawback for me, apart from the loss of freedom to do more or less what I want when I want on those days and that is having to drink instant coffee again, after several years without it. Someone once showed me years ago, that if you mix the instant coffee powder with milk before adding the hot water, the coffee tastes much better than if you don't. I agree that it does seem to but why would that be I wonder, when coffee is originally made by roasting coffee beans in heat?
    My latest forum article 'Australian Researchers Discover Potential Blue Green Algae Cause & Treatment of Motor Neuron Disease (MND)&(ALS)' Parkinsons's and Alzheimer's can be found at http://www.science20.com/forums/medicine
    Gerhard Adam
    ..if you mix the instant coffee powder with milk...
    Milk?!?!  That explains why your coffee doesn't taste as good as it smells.  That's drug abuse.  In this case the drug you're abusing is caffeine ... you're diluting it.  Poor caffeine ... :)
    Mundus vult decipi
    UvaE
    Milk?!?!  That explains why your coffee doesn't taste as good as it smells.  
    Yes the smell will be ruined, but adding milk is the best way to overcome coffee's bitterness and thus improve its taste. I love a little coffee with my milk...:)

    Gerhard Adam
    Bitterness?!?  Egads ... it's no wonder you guys have a problem with the taste.  That's like people complaining that their coffee might be too strong.  As if ....
    Mundus vult decipi
    Hank
    Yep, I go Double Black Diamond Extra Bold. Burn off all the caffeine, I don't care.  I never got into that coffee, even at the Cafe du Monde. I like the beignets, though.
    rholley
    I’ve also just now read this, another application of chitosan, to leather this time making use of its antimicrobial properties:

    Beating shoe smells with crab shells

    Robert H. Olley / Quondam Physics Department / University of Reading / England