Biorefinery and valorization of food waste and other
types of biomass
Food loss refers to all food produced for human consumption but not eaten by humans that is any food that
is lost in the supply chain between the producer and the market.
Food waste refers to food appropriate for human consumption being discarded, whether or not after it is
kept beyond its expiry date or left to spoil. Food is wasted in many ways such as:
 Fresh produce that deviates from what is
considered optimal in terms of shape, size
and color. For example fresh produce is
often removed from the supply chain during
sorting operations.
 Foods that are close to, at or beyond the
“best-before” date are often discarded by
retailers and consumers.
 Large quantities of wholesome edible food
are often unused or left over and discarded
from household kitchens and eating
establishments.
Algae
Food waste
Manure
Wheat
straw
Sugarcane
bagasse
Food waste in a global perspective
About 1.3 billion tonnes of food and one-third of the total global food production is wasted each year,
costing the world economy about $750 billion
Avoidable and unavoidable food waste
Food waste severely impact the environment due to emission of
greenhouse gases
The greenhouse gas emissions associated with food loss
and waste come from a variety of sources, including:
 On-farm agriculture emissions − including from the
digestive systems of cows, manure from livestock, onfarm energy use and fertilizer emissions − for
producing food that is ultimately lost or wasted.
 The production of electricity and heat used to
manufacture and process the food that is ultimately lost
or wasted.
 The energy used to transport, store and cook food that
is ultimately lost or wasted.
 The landfill emissions from decaying food.
 The emissions from land use change and deforestation
associated with producing food that is ultimately lost or
wasted.
Overview of multi-dimensional approaches
for valorization of food waste to value
added bio-based products in circular
bioeconomy
Schematic pathway of anaerobic
(absence of oxygen) fermentation
for bio-based products generation
Food waste and other types of biomass
Schematic illustration of an electro-fermentation device
Microorganisms
8
Schematic pathway for biodiesel production from oleaginous microorganisms
Biodiesel
Transesterification
9
Biorefinery of lignin
11
Biorefinery of lignin
Main building blocks of lignin
Lignin valorization
13
Bioplastic from food waste valorization
 Most commercial plastics are synthetic polymers derived from
petrochemicals and is a huge environmental problem for the ecosystems
as they tend to resist biodegradation and lead to the formation of
microplastic or nanoplastic.
 Polyhydroxyalkanoates (PHA)-derived plastics are attractive because
they are compostable and derived from renewables and are biodegradable.
 P3HB and other PHB’s (see below) are produced by certain
microorganisms in response to conditions of physiological stress, mainly
conditions in which nutrients are limited. PHB’s are primarily a product of
carbon assimilation (from glucose or starch) and are employed by
microorganisms as a form of energy storage molecules to be
metabolized when other common energy sources are not available.
The PHA biopolymer poly-3-hydroxybutyrate (P3HB)
is used for bioplastic production
Microplastics from synthetic
polymers constitute a huge
environmental problem
Production of
bioplastic through
food waste
valorization
Sources for different types of bioplastics/polymers
Bioplastic polymer chitin and chitosan
Chitosan bioplastic is biocompatible, biodegradable, easily molded into complex shapes, and inexpensive
because of the widespread availability of shrimp waste. Because of these beneficial characteristics, the
material is a potential replacement for conventional petroleum-based plastic in applications ranging from
consumer products to medical uses.
Secondary metabolites obtained from micro- and macroalgae and their uses
18
Microalgae
Macroalgae
19
Polyunsaturated fatty acids (PUFA) and carotenoids produced by microalgae
Reduce risk (preventive effect) for cardiovascular
diseases and chronic inflammation
Food colorants, pro-vitamin A source,
physiological modulators
20
Biosynthesis of prostaglandins
(important hormones)
ALA
GLA
Target for many
drugs
Essential fatty acids
Essential for the production of
prostaglandins. Humans cannot
synthesize these fatty acids. Can
only be provided through our diet)
21
General mechanism for inflammation
White blood cells (leukocytes)
Foreign bodies (antigens, bacteria, viruses, etc.)
Release of regulatory proteins (e.g., Nuclear factor (NF) -kB))
Binding of NF-kB to promoter on DNA for the formation of cytokines (e.g., Tumor necrosis
factor (TNF-α), interleukin (IL)-6)
Increased transcription of DNA into RNA = increased protein synthesis of e.g.,TNF-α, IL-6
TNF-α induce the formation of, for example, cyclooxygenase (COX)-2 and thus the
biosynthesis of prostaglandins (important regulatory hormones)
Prostaglandins signaling compounds for white blood cell assembly = Inflammation
Biosynthesis of prostaglandins, continued
23
COX
COX
COX
Cleavage of phycocyanobilin from phycocyanin (pigment in ‘blue green algae’) for
use in food colouring
24
Cyanobacteria
(‘blue-green algae’)
Reaction mechanisms for cleavage of phycocyanobilin (tetrapyrrole chromophore) by
solvolysis. In reactions with methanol R = CH3, and with ethanol R = CH2CH3
25
(A) Yields [mg g-1] of solvolysis reactions with ethanol 96%
v/v for different cleavage methods and temperatures.
(B) Purity [% w/w] obtained using different reaction methods.
(C) Yields [mg g−1] of solvolysis reactions with ethanol 96%
(v/v) for different reaction methods and reaction times.
Phycocyanobilins produced by solvolysis from phycocyanin
HPLC profile of solvolysis extract (sealed vessel)
27
Phycocyanobilins are strong electrophiles being able to react with thiol groups
in proteins, which may explain their potential anti-inflammatory and anticancer
effect
28
Utilization of fruit and vegetable waste
29
Dietary fibers
Dietary fibers constitute the portion of plant-derived foods that cannot be completely broken down by human
digestive enzymes but may to some extent be fermented in the gut by bacteria. Dietary fibers have two main
components, which are the water-soluble fibers and the water-insoluble fibers:
Soluble fibers, which are soluble in water and is readily fermented in the colon into gases and physiologically
active by-products, such as short-chain fatty acids produced in the colon by gut bacteria. Soluble fibers are
therefore also sometimes called prebiotic fibers, and delays gastric emptying which, in humans, can result in
an extended feeling of fullness. Typical examples of soluble fibers are:
 Arabinoxylan. Is a hemicellulose found in both the primary and secondary cell walls of plants, including
woods and cereal grains, consisting of copolymers of two pentose sugars: arabinose and xylose.
30
Dietary fibers
• Fructans. Are polymers built up of fructose residues, normally with a sucrose unit. Fructans with a short
chain length are known as fructooligosaccharides and the polysaccharides are called inulins. Fructans
occur in foods such as agave, artichokes, asparagus, leeks, garlic, onions (including spring onions),
yacón, jícama, and wheat.
Fructans
31
Dietary fibers
Pectin is a heteropolysaccharide, which is present in virtually all terrestrial plants where it helps to bind cells
together but is also found in primary cell walls. It consist of the partial methyl esters of polygalacturonic acid
and their salts (sodium, potassium, calcium, and ammonia), with a molecular weight of up to 150,000
Daltons. It is produced commercially as a white to light brown powder, mainly extracted from citrus fruits, and
is used in food as a gelling agent, particularly in jams and jellies, in dessert fillings, sweets, as a stabilizer in
fruit juices and milk drinks as well as in medicine.
32
Dietary fibers
Insoluble fibers does not dissolve in water and are inert to digestive enzymes in the upper gastrointestinal
tract and provides bulking. Some forms of insoluble fiber, such as resistant starches, can be fermented in the
colon. Bulking fibers absorb water as they move through the digestive system, easing defecation. Typical
examples of insoluble fibers are lignin, starch/resistant starch, cellulose and some hemicelluloses:
 Cellulose, is a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4)
linked D-glucose units. Cellulose is an important structural component of the primary cell wall of green
plants, and many forms of algae. Some species of bacteria secrete it to form biofilms. Cellulose is the most
abundant organic polymer on Earth. The cellulose content of cotton fiber is 90%, that of wood is 40–50%,
and that of dried hemp is approximately 57%.
Cellulose
33
Dietary fibers
34
 Starch is a form of dietary carbohydrate and is the form in which glucose is stored in plants. Chemically
speaking, it is a polysaccharide which is made up of monosaccharides (glucose/sugar molecules) that are
linked together. Starch is stored in compact granules consisting of two components amylose (soluble) and
amylopectin (insoluble). Resistant starch is resistant to digestion by the pancreatic enzyme, amylase. This
means that most of the starch makes it past the small intestine and through to the large intestine where it is
used in bacterial fermentation
Total dietary fibers (TDF), insoluble dietary fibers (IDF), soluble dietary fibers (SDF) contents
in the waste of different fruit and vegetables
35
Major types of secondary metabolites
present in some fruit and vegetables
wastes
36
Phenolic acids
Lignin (stained with blue color)
Lignans – dimers of phenolic acids
Flaxseed
Cereals
Flavonoids and stilbenoids
Flavonoids
41
Flavonoids
OH
OH
OH
OH
HO
42
O
O
GlcO
−
O-Glc Rha
OH
Quercetin 3-O
OH
O
-rutinosid (rutin, flavonol)
O
Luteolin 3- -glucosid (flavon)
O
OH
OH
OH
OCH3
O
GlcO
Green tea
(Camellia sinensis)
HO
O
OH
OH
Hesperetin 7-O
O
-rutinosid (flavanon)
OH
(+)-Catechin (flavan-3-ol)
Flavonoids are widely distributed in plants
Flavonoids have been used in the food industry due to their
ability to preserve foods, to provide colour and flavour and to
make dietary supplements, among other important industrial
applications.
Citrus fruits such as
sweet oranges, lemons,
grapefruit, limes, and
so on
Resveratrol an effect on lifestyle diseases?
used as a nutraceutical
OH
HO
OH
Resveratrol
Peanuts
Grapes/red wine
43
Carotenoids
Flavoring agents and aroma produced from fruit and vegetable waste using
microorganisms (fermentation)
Ethyl butyrate
Isoamyl acetate
Vanillin
(R)-(+)- and (S)-(−)-γDecalactone
Organic acids produced from fruit and vegetable waste using microorganisms (fermentation)
Acetic acid
Citric acid
Lactic acid
Enzymes produced from fruit and vegetable
waste using microorganisms (fermentation)
Amylase
An enzyme that catalyses the
hydrolysis of starch into sugars
Article review (repetition from September 3)
Focus on review of articles and writing of scientific papers
Articles are usually composed of an Abstract, Introduction, Materials and Methods (Experimental),
Results, Discussion (sometimes combined) and Conclusion/perspective and finally References/
literature.
Introduction
This is the most important part of an article especially in the writing phase.
 The introduction should give a relevant background of the study in a broad perspective citing the most
important literature within the subject and should contain: (1) aim/purpose of the study and/or (2) a
hypothesis that is substantiated by the information given in the introduction. (1) and (2) can instead be
replaced by relevant questions and then the article will provide suitable answers to the questions based
on the results.
 Introduction can/should be used as an outline for the whole articles and should have a clear focus. Avoid
investigations in the same article that are too different and therefore are not complementary.
Materials and Methods
Should contain a description of the most important techniques and materials used. Often researchers refer to
previous work in order to avoid repetition of well known or previous described methods. Depends also on the
journal. Also important that the statistics is properly designed and executed.
Article review (repetition from September 3)
Focus on review of articles and writing of scientific papers
Results
Most important results are presented in this part. If the Results and Discussion is not combined the
results are not discussed in this part. However, minor comments to the results can be included in this part
if relevant.
Discussion
In the Discussion, the results are discussed in relation to the aim/purpose, hypothesis or questions given
in the introduction. In the Discussion section the results are also discussed in relation to the present
scientific knowledge in the field by including relevant scientific literature. In addition, the results are
sometimes put in a broader perspective.
Conclusion
The most important results of the scientific study is briefly described and the impact of the results of the
study.
In an article one should be as correct as possible avoiding typing errors and contradictions, to be
consistent in the use of scientific designations and to use them correct, avoid unverifiable statements
(speculations) or statements that are not substantiated by the results in the article.
In connection with your Critical Review of articles in this course you should focus
on:
•
•
•
•
Significance/contribution to the field
Methodology /approach
Arguments & use of evidence
Writing style & text structure
The above points will be addressed and discussed in more detail in some of the other lectures in this
course and are important when you prepare you Critical Review for the exam. I admit that most of
you do not have the background for evaluating all these points in the article we will discus in my part
of the course but at the exam the material/articles you will have to evaluate through a Critical Review
the above points will all be relevant.
Article reviews of the following articles (online discussions – see also attached
notes):
Article no. 1
Bioactive Phenolic Compounds from the Agroindustrial Waste of Colombian Mango Cultivars
‘Sugar Mango’ and ‘Tommy Atkins’— An Alternative for Their Use and Valorization. Antioxidants
2019, 8, 41, 1−19.
Article no. 2
Vitis vinifera ‘Pinot noir’ leaves as a source of bioactive nutraceutical compounds. Food Funct.
2019, 10, 3822–3827.