Added-value processing of ‘algae waste': 2nd quarterly report

Added-value processing of ‘algae waste': 2nd quarterly report

Background - This second report provides an update of information and interim results for a two year study being conducted at the Satake Centre for Grain Process Engineering in the University of Manchester, investigating the feasibility of producing value-added products from algae.

Project Aim - To examine in detail and optimise the production of generic fermentation feedstocks from algae wastes and evaluate the feasibility of producing a range of potential end-products (in particular ethanol and algae nutrients).

Achievements to Date - Process development and design: The materials under investigation were two feedstocks of microalgae sent by Cellana on 13th January 2010 (samples 1323 and 1584). Currently, the algae are harvested by centrifugation or spray-drying, and lipids are then extracted using hexane. At UoM, various process scenarios to produce glucose were tested: fermentation with Aspergillus awamori, fermentation with indigenous microorganisms, acid hydrolysis and enzymatic hydrolysis. All the data accumulated with the different strategies were used to develop flowsheets that can help to estimate the ethanol production for each scenario.

The characterisation work enables to conclude that both samples differ by their lipids and other chemicals content. In this work, a variety of indigenous microbes were also isolated from both samples, and such microbes now form part of a culture collection.

Pre-treatment of unextracted samples: As part of process development and design, various techniques were tested to disrupt the algae in order to facilitate access to lipids and carbohydrates without the utilization of hexane. The use of a physical and biological disruption method to break open the cells would have the advantage to be a cleaner process as no chemical will be involved. Consequently, the lipids could be harvested by skimming the oil layer at the surface of the cell suspension. Several cell disruption methods were tested: mortar and pestle, bead mill, liquid nitrogen, autoclaving, microwaving, falling number hammer mill, ultrasound and French press. It was found that ultrasound and the French press were the most effective methods. Further tests are needed to determine if an oil layer can be obtained at the surface after these 2 pre-treatments.

From the process point of view, the acid hydrolysis treatment involves simultaneous cell-disruption and saccharification, which can take place in the same unit. However, lipids and proteins degradation could occur.
There were no benefits associated with the use of A. awamori for breaking the cells open, releasing lipids or glucose, and converting carbohydrates into glucose.

Fermentation process: The highest glucose production was achieved with indigenous microbes degrading ultrasound-treated and untreated samples. Sample 1584 had higher lipid and carbohydrates content and gave greater glucose production during indigenous fermentation (55 mg of glucose per gram of sample).

Since the best performances (in terms of glucose) were obtained with the indigenous microbes degrading the raw sample, it can be concluded that no further pre-treatment is required before the microbial conversion step.

Depolymerisation process: A detailed account of experiments with commercial enzyme is presented in this part, whereby algal samples with or without cell-disruption treatment were used as feedstock in parallel experiments to enzymatically produce glucose. Although enzyme addition increases glucose production its contribution is thought to be low.

Combined fermentation-depolymerisation process (indigenous microorganisms and added enzyme) with and without treatment:
Sample 1584 produced the highest levels of glucose and the best results were observed when the indigenous microbes were mixed with enzymes. After 100 hours of running the experiment, glucose was not consumed and remained approximately constant until the end of the experiment.

With the best combination of processes, about 27% of total carbohydrates in sample 1323 was converted into glucose whereas, in the case of the disrupted sample 1584, about 55% was converted into glucose by indigenous microbes and 60% by combining indigenous microbes and enzymes. This investigation gives grounds to decide if commercial enzymes and cell-disruption pre-treatment is economically interesting.

In the case of fermentation and enzymatic hydrolysis, a pre-treatment step might be required to facilitate the conversion of carbohydrates. This should be followed by the depolymerisation of carbohydrates into simple sugars.
Preliminary results with samples D09 and D10: Progress has been gained working with the new unextracted feedstocks sent by Cellana (D09 and 10) on February. The Characterisation work is undergoing and it has been found that glucose can be produced from D09 and D10 when treated with indigenous microorganisms from samples 1323 and 1584. Noteworthy is to mention that D09 and D10 also contain their own indigenous microbes but, in this case, such microbes produced and consumed glucose.

Culturing the oleaginous yeast R. toruloides: This aims at growing oleaginous yeast to extract the oil. In one project, the algae by-product will serve as substrate to grow the yeast whereas a synthetic substrate will be used in the second project. The plan of actions and the time to achieve the goals is presented (Gantt chart).

Literature review: An introduction to algae is presented and is followed by a review on the properties of the algal biomass. An account of the cultivation methods and productivity is also given. Besides, there is a summary of upstream processes employed to eliminate water from the harvested algae. Finally, the review presents an account of the extraction and purification of added-value products such as biodiesel, bioethanol, biomethane and other bioactive compounds and fine chemicals.

Other deliverables and task on hold: A culture collection of known microbes is now available at UoM. Another task that has been put on hold is the growth of Nannochlorepsis sp, which was the model chosen for growing microalgae with the fermentation products from A. awamori and A. oryzae.

Overall progress - More realistic numbers in terms of ethanol production have been obtained and are presented in the process development and design spreadsheets. Further improvements will be gained with new experimental results.
The search for a physical disruption method is now concluded. More tests are needed to determine if an oil layer can be obtained at the surface after ultrasound or French press treatment.

Samples 1323 and 1584 have been characterised and therefore this task is finished. On the other hand, chemical and biological methods to produce glucose have been tested in samples 1323 and 1584. Similar work has been done with D09 and D10 and the results reported herein show that glucose can be produced from these samples when treated with indigenous microbes from 1323 and 1584.

The depolymerisation process of 1323 and 1584 is finished but it still needs to be deployed to treat algae D09 and D10. Enzyme, indigenous microbes and a combination of both need to be studied in the disrupted D09 and D10. There is now a plan of actions and timing for growing oleaginous yeast with algae or a synthetic medium.

Confidential.