Tasty or deadly fruits: A PhD thesis!

Fruits is probably just something to eat. But, it has a special function in reproduction of the trees by carrying the seeds. The fruits should be on trees for a some weeks or months and keep safe against the continual bacterial attacks. That is where the flavors comes into the picture. One of their important functions is to keep the fruits safe until matured.

We have globally more than 400 million tons fruits waste every year, that is perfect to be converted to biogas and produce energy. However, these flavors can become problem and when you put them in the reactor, they can kill the cells even in very low concentrations. What are these flavors, how toxic they are and how to treat them, is a subject of PhD thesis by Rachma Wikandari. She is defending her thesis in a couple of weeks on 27 Nov. Here is the details of her work:

PhD thesis: Effect of fruit flavors on anaerobic digestion: inhibitions and solutions

and publications:

1. Inhibitory effects of fruits flavors on methane production during anaerobic digestion

2. Ester compounds on biogas production: beneficial or detrimental? 

3. Effect of Ketone, Lactone, and Phenol on Methane Production and Metabolic Intermediates during Anaerobic Digestion

4. Improvement of biogas production from orange peel waste by leaching of limonene

5. Performance of semi-continuous membrane bioreactor in biogas production from toxic feedstock containing D-limonene

6. Biogas Production from citrus waste by membrane bioreactor

PhD thesis: Simultaneous Saccharification, Fermentation and Filtration (SSFF)

Our PhD student Mofoluwake Ishola will defend her thesis on "Novel application of membrane bioreactors in lignocellulosic ethanol production : simultaneous saccharification, filtration and fermentation (SSFF)" on 31 October. She had nailing today which an old tradition (since 1517 by Martin Luther). In this ceremony, the candidate nail the thesis on a tree as you can see in the photo.

The thesis was about fermentation of lignocellulosic materials. She developed a method that combines the traditional methods of enzymatic hydrolysis and fermentation named Simultaneous saccharification and fermentation (SSF) and separation hydrolysis and fermentation (SHF) to this new method called SSFF. Using membranes are the heart of this development.  You can read more about it in her thesis, or publications: 

- Simultaneous saccharification, filtration and fermentation (SSFF): A novel method for bioethanol production from lignocellulosic biomass
- Effect of high solids loading on bacterial contamination in lignocellulosic ethanol production,
- Effect of Fungal and Phosphoric acid Pretreatment on Ethanol production from Oil Palm Empty Fruit Bunches (OPEFB)
- Biofuels in Nigeria: A critical and strategic evaluation,

Cooking egg on biogas from palm oil residuals

I have recently visited our projects in Indonesia that deals with biogas from palm oil residuals. At a palm oil plant in Borneo, FOV Biogas installed a 100 m3 pilot that is producing biogas from POME (palm oil mill effluent) in a textile reactor. In a parallel project, in a lab textile reactor at Gadjah Mada University, OPEFB (Oil Palm Empty Fruit Bunches) are converted to biogas. Our Indonesian student (Luki) with his colleague are happily cooking egg for their lunch from the biogas that they have produced  from OPEFB. I tasted the egg, and it was quite good :)

(The students are cooking egg from the biogas produced in textile reactor from OPEFB. You can see some OPEFB on the reactor)

(The textile reactor for converting biogas from POME)

A shortcut to commercial second generation ethanol using fungi

Ethanol is produced today by the 1st generation processes, e.g. from sugarcanes in Brazil or grains in the USA. It is now about 3 decades with intensive research and development on the 2nd generation ethanol from lignocelluloses, but the process is not commercial yet.

We have a concept to integrate the lignocelluloses into the 1st generation ethanol plants from grains by filamentous fungi, a concept that we are developing since 1999. It means, several hundreds of dry mils (ethanol from grain processes) can already start producing ethanol from lignocelluloses with principally very low investment. By this integration, ethanol and animal feed are produced from stillage (wastewater of the process) and also added lignocelluloses materials. The concept is now examined in large fermentors in the large ethanol plant in Sweden (Agroetanol) and can hopefully make the lignocelluloses ethanol closer to commercial market. You can download the scientific publication about it here!

  (An integrated first and second generation ethanol process. The integration could occur at the fermentation step, or at the proposed fungal cultivation step)

Membranes Bioreactor or capsules for ethanol production? A PhD thesis

On 4th April, our PhD student Päivi Ylitervo will defend her thesis. She had the goal to develop rapid fermentation of toxic wood hydrolyzates for ethanol production. Her work was in parallel of another PhD study on "Suiciding yeast" that I mentioned last month. She worked on capsules in half of her work, and then focused on membrane bioreactors for ethanol production. It is an interesting and novel work, considering the membrane bioreactors are developed principally for wastewater treatment. It gives a new application for such bioreactors. Let's wish her good luck in her defense!

Her thesis on "Concepts for improving ethanol productivity from lignocellulosic materials: encapsulated yeast and membrane bioreactors", can be found here!

Some of her publications:

Päivi Ylitervo, Carl Johan Franzén, Mohammad J. Taherzadeh,(2011), Ethanol production at elevated temperatures using encapsulation ofyeast, Journal of Biotechnology, 156, 22 – 29

Päivi Ylitervo, Carl Johan Franzén, MohammadJ. Taherzadeh, (2013), Mechanically robust polysiloxane-ACA capsulesfor prolonged ethanol production, Journalof Chemical Technology & Biotechnology, 88, 1080–10

Päivi Ylitervo, Carl Johan Franzén, Mohammad J. Taherzadeh, (2013),Impact of furfural on rapidethanol production using a membrane bioreactor, Energies, 6,1604-1617

Päivi Ylitervo, Julius Akinbomi,Mohammad J. Taherzadeh (2013), Membrane bioreactors’ potential for ethanol and biogas production: Areview, Environmental Technology, 34: 1711–1723 

A PhD thesis on Membranes for bioreactors

This week, we will have our third PhD defense in three weeks (one defense per week). The last two defenses went quite well, and I hope this last one will also go well. This time, our PhD student Hamidreza Barghi will defend his thesis that is about making membranes for membrane bioreactors. These membranes are quite specific. They have to retain the cells, while being permeable to the cells feed (substrates) and their products (metabolites), the gases (such as CO2, and methane), and they have to resist the harsh conditions in the reactors.

The thesis can be downloaded here!

Why big digesters for biogas? A PhD thesis

If you have seen biogas processes, you have probably noticed very big vessels for the biogas productions. They are normally 100-10,000 m3 in size. The reason of this big size is that the materials should stay in the reactors for about 30 days. The bugs that do the job and produce biogas are sensitive and need long time to grow. Just as example, you can compare E. coli bacteria that can duplicate itself in 20 minutes, while a methane producing bacteria (or archaea) need about 2 weeks to duplicate. It means if you don't want them to get away from the reactor, you should have big vessels, feed it slowly and let them to stay longer than two weeks.

In a PhD thesis that will be defended 27 Feb. 2014, Solmaz Aslanzadeh found a method to reduce this retention time from about 30 days to about 6 days! It means if her results can be applied commercially, the biogas digesters will squeeze by 80% in their size. You can read her thesis to see how she did it:

Thesis title: Pretreatment of cellulosic waste and high rate biogas production

Chemical reactions in biogas fermentation

Biogas (or biomethane) production looks simple. Just put the materials and the digesting bacteria into a vessel, and let them take care of the rest and produce the biogas. They have done it for probably billions of years, and in industries today it is still the same.

However, if operators of a biogas plant do not follow the recommendations or do not know how to run a biogas plant, the chance of failure would be quite high. It is in fact one of the reasons that the numbers of biogas plants are not boosted globally. The point here is that we have many microorganisms (bacteria and archaea) that live perfectly together in a society. In a recent work, we have defined about chemical 50 reactions that occur in parallel and series and affect each other. These reactions were modeled using ASPEN Plus and checked against with several data available from experimental works and also industries. If you are investigating about biogas, this article and the original model (in ASPEN) could be interesting for you:

Rajendran, K., Kankanala, H.R., Lundin, M., Taherzadeh, M.J. (2014): A Novel Process Simulation Model (PSM) for Anaerobic Digestion Using Aspen Plus, Bioresource Technolology:
Available at:

http://www.sciencedirect.com/science/article/pii/S0960852414000765

and the model and prepublished article at:
http://bada.hb.se/handle/2320/12358  

Suiciding yeast? a PhD thesis

Since several years ago, we realized that if we put baker's yeast in a capsule, they have better performance in toxic media for e.g. ethanol production. It means that if they are together in a packed form, they can stand against the inhibitors. To find out the reason for this phenomenon was the question in this PhD thesis. In simple word, the yeast cells that are in the outer layer, are killed to protect the cells that are in the inner layers that can grow and eventually replace the dead cells in the outer layers. It is probably the same method used in classical wars or by larger organisms such as penguins in cold and windy polar climates!

Thesis by PhD candidate Johan westman (to be defended 19 Feb. 2014):
Ethanol production from lignocellulose using high local cell density yeast cultures. Investigations of flocculating and encapsulated Saccharomyces cerevisiae 

(Encapsulated yeast- photo by Johan westmant)