Hot water extraction and membrane filtration processes in fractionation and recovery of value-added compounds from wood and plant residues
Almanasrah, Mohammad (2017-03-16)
Väitöskirja
Almanasrah, Mohammad
16.03.2017
Lappeenranta University of Technology
Acta Universitatis Lappeenrantaensis
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-335-058-8
https://urn.fi/URN:ISBN:978-952-335-058-8
Tiivistelmä
The production of green chemicals and sustainable energy from renewable resources is gaining
global interest. Special attention is paid to the refining of biomass residues, e.g. forest and
agricultural wastes, into high value bio-based products. However, although biomass residues
contain many valuable extractable compounds, their complex nature makes their full exploitation
challenging. To overcome such difficulties, the development of efficient extraction, fractionation,
concentration, and purification processes for the recovery of good quality natural-based
biochemicals and biopolymers is essential. The aim of this study is to develop sustainable
separation processes that could be applied on a large scale for the recovery of high value-added
compounds from various kinds of biomass residues.
In the first part of this work, an ultrafiltration (UF)-based separation process was performed for
the recovery and fractionation of galactoglucomannans (GGMs) from spruce autohydrolysates.
The evaluation of different membrane materials showed that the regenerated cellulose (RC)
membranes (10 and 30 kDa) could offer rather high permeability of autohydrolys with a quite low
fouling tendency. The purity of the GGMs in the hemicellulose fractions after UF was from 60 to
80%, and the concentration of hemicelluloses reached even 400 g/L. This was achieved by using
hydrophilic membranes and a high shear rate filter. The average molar masses of the different
concentrates were from 5 to 18 kDa. These specifications provide great potential for the
concentrated fractions to be utilized as raw material for manufacturing e.g. sustainable packaging
films and hydrogels.
In order to purify the rich fractions of the GGMs further, diafiltration (DF) and oxidation were
applied. Diafiltration of concentrated fractions containing high molar mass GGMs leads to the
increase of their average molar mass by removing small molar mass compounds. The results also
proved that only partial removal of lignin could be achieved by DF. Oxidation of the
autohydrolysates improved the purity of the GGMs slightly, although the total amount of phenolic
compounds (lignin) was not decreased notably. Mainly lignans and wood extractives were
degraded by the oxidation. Oxidation increased the filterability of the autohydrolysates
significantly, mainly due to the decrease of the viscosity of the oxidized autohydrolysates. This indicates that some changes in high molar mass compounds occurred in the oxidation process,
which had a clear effect on the viscosity and filterability of the autohydrolysate.
In the second part of this work, nonedible carob residues were processed in a hybrid separation
process consisting of aqueous extraction and membrane-based separation techniques. This process
aimed at extracting phenolic compounds and sugars from carob kibbles, and then fractionating and
concentrating these value-added compounds from the aqueous extracts. One-step extraction
recovered only about 20% of the phenolic compounds, but the extract contained a significant
amount of sugars (110 g/L). The membrane-based separation of phenolic compounds and sugars
from this extract was inadequate. Therefore, two-step aqueous extraction at different temperatures
(30 and 100 °C) was developed. It gave a superior yield of phenolic compounds, i.e. about 70%.
It also upgraded the quality of the extracts obtained from the carob residues by improving the
separation of the sugars from the phenolic compounds in the extraction stages. By the membrane
processes, two distinct natural streams from carob kibbles could be produced. The first stream is
enriched in antioxidant content, namely catechin and its derivatives, for the nutraceuticals market.
While the second stream is enriched in sugars for the food industry. In addition, the proposed
process, including the two-step extraction process combined with nanofiltration (NF) and reverse
osmosis (RO) fulfils the zero-discharge principle.
Hybrid processes based on combining membrane filtration with aqueous extraction could
effectively be applied as a sustainable recovery and separation approach in biorefinery. This
approach utilizes the environmental benefits of water as a green solvent to upgrade the exploitation
of biomass residues. The proposed hybrid process is able to scale up and extend to other biomass
residues, which makes it a promising alternative when biorefinery processes are developed and
implemented.
global interest. Special attention is paid to the refining of biomass residues, e.g. forest and
agricultural wastes, into high value bio-based products. However, although biomass residues
contain many valuable extractable compounds, their complex nature makes their full exploitation
challenging. To overcome such difficulties, the development of efficient extraction, fractionation,
concentration, and purification processes for the recovery of good quality natural-based
biochemicals and biopolymers is essential. The aim of this study is to develop sustainable
separation processes that could be applied on a large scale for the recovery of high value-added
compounds from various kinds of biomass residues.
In the first part of this work, an ultrafiltration (UF)-based separation process was performed for
the recovery and fractionation of galactoglucomannans (GGMs) from spruce autohydrolysates.
The evaluation of different membrane materials showed that the regenerated cellulose (RC)
membranes (10 and 30 kDa) could offer rather high permeability of autohydrolys with a quite low
fouling tendency. The purity of the GGMs in the hemicellulose fractions after UF was from 60 to
80%, and the concentration of hemicelluloses reached even 400 g/L. This was achieved by using
hydrophilic membranes and a high shear rate filter. The average molar masses of the different
concentrates were from 5 to 18 kDa. These specifications provide great potential for the
concentrated fractions to be utilized as raw material for manufacturing e.g. sustainable packaging
films and hydrogels.
In order to purify the rich fractions of the GGMs further, diafiltration (DF) and oxidation were
applied. Diafiltration of concentrated fractions containing high molar mass GGMs leads to the
increase of their average molar mass by removing small molar mass compounds. The results also
proved that only partial removal of lignin could be achieved by DF. Oxidation of the
autohydrolysates improved the purity of the GGMs slightly, although the total amount of phenolic
compounds (lignin) was not decreased notably. Mainly lignans and wood extractives were
degraded by the oxidation. Oxidation increased the filterability of the autohydrolysates
significantly, mainly due to the decrease of the viscosity of the oxidized autohydrolysates. This indicates that some changes in high molar mass compounds occurred in the oxidation process,
which had a clear effect on the viscosity and filterability of the autohydrolysate.
In the second part of this work, nonedible carob residues were processed in a hybrid separation
process consisting of aqueous extraction and membrane-based separation techniques. This process
aimed at extracting phenolic compounds and sugars from carob kibbles, and then fractionating and
concentrating these value-added compounds from the aqueous extracts. One-step extraction
recovered only about 20% of the phenolic compounds, but the extract contained a significant
amount of sugars (110 g/L). The membrane-based separation of phenolic compounds and sugars
from this extract was inadequate. Therefore, two-step aqueous extraction at different temperatures
(30 and 100 °C) was developed. It gave a superior yield of phenolic compounds, i.e. about 70%.
It also upgraded the quality of the extracts obtained from the carob residues by improving the
separation of the sugars from the phenolic compounds in the extraction stages. By the membrane
processes, two distinct natural streams from carob kibbles could be produced. The first stream is
enriched in antioxidant content, namely catechin and its derivatives, for the nutraceuticals market.
While the second stream is enriched in sugars for the food industry. In addition, the proposed
process, including the two-step extraction process combined with nanofiltration (NF) and reverse
osmosis (RO) fulfils the zero-discharge principle.
Hybrid processes based on combining membrane filtration with aqueous extraction could
effectively be applied as a sustainable recovery and separation approach in biorefinery. This
approach utilizes the environmental benefits of water as a green solvent to upgrade the exploitation
of biomass residues. The proposed hybrid process is able to scale up and extend to other biomass
residues, which makes it a promising alternative when biorefinery processes are developed and
implemented.
Kokoelmat
- Väitöskirjat [1037]