Bioresource Technology 81 (2002) 91±96
Plant growth-promoting oligosaccharides produced
from tomato waste
Toshisada Suzuki a, Kaori Tomita-Yokotani b,*, Hirokazu Tsubura c, Shigeki Yoshida b,
Isao Kusakabe b, Kosumi Yamada b, Yoichi Miki d, Koji Hasegawa b
a
Doctoral Degree Program in Agricultural Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
b
Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
c
Research Institute, KAGOME Co., Ltd., Nishinasuno, Tochigi 329-0027, Japan
d
Miki Ltd., Sapporo Nishiku, Hokkaido 063-0849, Japan
Received 5 May 2001; received in revised form 26 June 2001; accepted 18 July 2001
Abstract
Tomato juice waste was hydrolyzed with acid. Tomato juice waste (500 g; wet weight) was heated with 0.5 N HCl (2.5 l) at 70 °C
for 4 h. After neutralization, the growth-promoting extracts (300 g; dry weight) in the plants were produced from the tomato waste.
The acid extract signi®cantly promoted the growth of cockscomb (Celosia argentea L.) and tomato (Lycopersicon esculentum L.)
seedlings. We have recognized potent plant growth-promoting substances in the acid extract from tomato waste. The most e€ective
components in the active fraction were almost all oligogalacturonic acids (DP 6±12). This paper is the ®rst report that plant growthpromoting oligosaccharides can be directly produced from tomato juice waste. It is possible that the substances from the tomato
waste can become useful plant growth regulators in the agriculture ®eld in the future. Ó 2001 Elsevier Science Ltd. All rights
reserved.
Keywords: Acid oligosaccharide; Food industry; Growth-promoting substance; Lycopersicon esculentum; Oligogalacturonic acid; Solanaceae;
Tomato juice; Waste
1. Introduction
Tomato juice is well known as a healthy beverage. It
contains a large amount of lycopene and carotenoids,
which decrease the risk of some diseases or various
types of cancers (Bramley, 2000; Rao and Agarwal,
2000; Sharoni et al., 2000). In Japan, more than 80 000
tons of tomato juice is produced in the food industry
each year. The production of tomato juice and vegetable
juice has increased year by year due to interest in health,
but at the same time, the amount of wastes has also
increased.
In tomato juice processing, the tomato is ®rst crushed, heated at 70 °C and ®ltered. After the ®ltering, a
great deal of the waste, peel, seed and jelly matter are
produced. The amount of wastes from tomato juice is
estimated at several thousand tons in Japan. At present,
*
Corresponding author. Tel.: +81-298-53-4617; fax: +81-298-537229.
E-mail address: [email protected] (K. TomitaYokotani).
most of the waste is dumped at a large expense. Therefore, it is desired that new products produced from the
tomato juice waste are found and that the cost of
dumping the waste is reduced.
Several researchers have studied using tomato waste
as feed for broiler chicks or ®sh (Squires et al., 1992;
Ho€man et al., 1997), and have produced something
with value from the waste. Lycopene and carotenoids as
food colorants have been extracted from tomato waste
using organic solvents (Chandler and Schwartz, 1987;
Tan, 1988; Heinonen et al., 1989; Sadler et al., 1990;
Khachik et al., 1992; Hakala and Heinonen, 1994;
Tonucci et al., 1995). Baysal et al. (2000) reported that
lycopene and b-carotene were extracted more e€ectively
from tomato paste waste using supercritical carbon dioxide. Furthermore, seed oil has also been extracted
from tomato juice waste (Sogi et al., 1999). The oil expelled from these tomato seeds showed physical as well
as chemical characteristics similar to any conventional
oil.
These methods e€ectively reused the tomato waste,
however, they have not been adopted in Japan. There
0960-8524/02/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved.
PII: S 0 9 6 0 - 8 5 2 4 ( 0 1 ) 0 0 1 2 4 - 9
92
T. Suzuki et al. / Bioresource Technology 81 (2002) 91±96
are four reasons why we have to consider reuse of the
tomato juice waste:
1. the waste is discharged seasonally in a large quantity,
2. the waste contains much water, and preservation is
dicult,
3. the waste is composed of low nutritive value materials
such as peel, seed and jelly matter and
4. the demand of produced lycopene and carotenoids or
seed oil might be low.
On the other hand, it has the potential that plant
growth-promoting substances could be produced from
tomato juice waste, since the waste includes many
polysaccharides, and some reports suggested that fragments of polysaccharide promote the growth of some
species of plant (Adachi et al., 1988; Fry et al., 1993;
Yonemoto et al., 1993; Natsume et al., 1994; Yamaguchi
et al., 1996). In this study, we attempted to produce
some plant growth-promoting substances from the tomato juice waste and discussed the possibility of the
e€ective reuse of such waste.
2. Methods
2.1. Materials
The tomato juice waste (water content approximately
75%) was obtained from Kagome Company, Japan.
Tri¯uoroacetic acid (TFA) was purchased from Sigma
Chemical. Sodium cyanoborohydrate was obtained
from Aldrich Chemical. All other chemicals were from
Wako Pure Chemical Industries, Japan.
2.2. Extraction
The tomato waste (20 g; wet weight) was heated with
100 ml of H2 O at 70 °C for 4 h. After the treatment, the
waste solution was ®ltered and the ®ltrate was adjusted
to pH 7.0 with 1 N NaOH. The sample was reduced in
vacuo at 40 °C to give a concentrate (20 ml) and the
concentrate was partitioned three times with equal volumes of ethyl acetate (EtOAc). The EtOAc fraction
showed an inhibitory activity. The water fraction was
concentrated to dryness in vacuo to produce a grey
powder, and designated as the water extract (WE).
Additionally, the same amount of tomato waste was
heated with 100 ml of 0.5 N HCl at 70 °C for 2, 4, 6 and
8 h, treated as before and designated as the 2, 4, 6 and 8
acid extract (AE) fractions, respectively.
2.3. Determination of the amounts of inorganic substances
The most biologically e€ective extract, the 4 h acid
extract (4AE), was burnt to ash in a crucible at 525 °C
for 12 h. After the ash was cooled, adequate H2 O was
added to it. The amount of inorganic substances in the
extract was determined using inductively coupled
plasma atomic emission spectroscopy (ICP: P-400,
Hitachi).
2.4. Puri®cation of 4AE
Five hundred grams of tomato juice waste (wet
weight) was heated with 2.5 l of 0.5 N HCl at 70 °C for 4
h, followed by ®ltration. The ®ltrate was adjusted to pH
7.0 with 1 N NaOH. The sample was evaporated in
vacuo at 40 °C to give a concentrate and the concentrate
was partitioned three times by equal volumes of EtOAc.
The water layer was concentrated to dryness in vacuo to
give a grey powder. The amount of the powder was
approximately 300 g. One hundred grams of the sample
was dissolved in 100 ml of H2 O and chromatographed
on an anion exchange column …/5 15 cm† (Q Sepharose FF, Pharmacia biotech) with H2 O and 0.1% TFA
(1000 ml/step). This operation was repeated three times.
During screening for plant growth-promoting substances, the cockscomb (Celosia argentea L.) test was
used since it has been found that the cockscomb shoot is
highly sensitivity to growth-promoting substances
(Hasegawa et al., 1992). The fractions from the 0.1%
TFA eluent were combined and concentrated to 300 ml
of solution in vacuo. Five times the volume of methanol
was added to the concentrate, and centrifuged at 3000
rpm for ten minutes. The precipitate was dissolved in
100 ml of H2 O and the solution was fractionated into
four parts; Mr above 105 , from 105 to 104 , from 104 to
103 and below 103 by ultra®ltration (Novacell 150,
Filtron). The biological activity was detected in the Mr
fraction from 104 to 103 . This active fraction was then
lyophilized. The lyophilized sample (25 mg) was dissolved in 25 ml of H2 O, and puri®ed by gel chromatography (Bio-Gel P-10 Bio-Rad, /16 400 mm, H2 O,
0.3 ml/min, 210 nm detector). Biological activity was
detected between the retention times of 60 and 120 min,
this fraction was then lyophilized (16 mg of white
powder) for further analyses.
2.5. HPAEC-PAD
The biologically active fraction from the gel chromatography was analyzed by an HPLC system (model
305, Gilson) with an HPAEC-PAD. HPAEC-PAD was
performed on a Carbopac PA-1 column (/4 250 mm,
Dionex), and detected using a pulsed amperometric
detector (PAD) equipped with a gold working electrode.
The ¯ow rate was 0.8 ml/min. A linear gradient from
H2 O to 80% 0.5 M oxalate bu€er, pH 6.0, was applied
from 0 to 10 min, and a linear gradient from 80% to
100% was from 10 to 20 min. To facilitate the detection
of carbohydrates, 500 mM NaOH was added to the eluate at the ¯ow rate of 0.5 ml/min.
T. Suzuki et al. / Bioresource Technology 81 (2002) 91±96
2.6. Determination of the amount of neutral and uronic
acid sugars in the HPAEC-PAD eluate
To determine the sugar content, the puri®ed eluate
from HPAEC-PAD was fractionated into 0.4 ml portions without NaOH addition. The carbohydrate and
uronic acids in the eluates were assayed by the phenol±
H2 SO4 (Dubois et al., 1956) and m-hydroxybiphenyl
methods (Blumenkrantz and Asboe-Hansen, 1973), respectively. The neutral sugar and uronic acid contents
were calculated as follows:
Neutral sugar …mg=ml† ˆ 92:2 ‰A490
0:464 A520 Š
Uronic acid …mg=ml† ˆ 112:4 ‰A520
0:0272 A490 Š
A490 is the absorbance at 490 nm for the phenol±sulfuric
method; A520 is the absorbance at 520 nm for the mhydroxybiphenyl method.
2.7. Determination of sugar composition
Ten lg of the sample was dissolved in 100 ll of 4 M
TFA in a glass tube. The tube was tightly sealed and
incubated at 100 °C for 6 h. The tube was then cooled to
room temperature and TFA in the sample was removed
by an evaporator. The dried sample and standard sugars
(Ara, arabinose; Gal, galactose; GalUA, galacturonic
acid; Glc, glucose; GlcUA, glucuronic acid; Man,
mannose; Xyl, xylose) were reacted using the ABEE
reagent (Kwon and Kim, 1993; Sun et al., 1997). The
reacted samples (100 ml) were analyzed by HPLC with a
Honenpak C18 column (/4:6 75 mm; Honen) at
30 °C. Chromatography was performed in the isocratic
mode with 0.2 M sodium boric bu€er (pH 8.9)/acetonitrile (ˆ 93:7) at the ¯ow rate of 1.0 ml/min. The
ABEE-sugar derivatives were detected at 305 nm.
2.8. Bioassay
Eight cockscomb (C. argentea L.) seeds were placed
on a ®lter paper moistened with 0.5 ml of test solution in
a 33 mm Petri dish. The Petri dishes were kept in the
dark at 25 °C for four days, and then the shoot and root
lengths were measured. For tomato (Lycopersicon esculentum L.) assay, the seeds were ®rst spread evenly on
93
a wet ®lter paper in a tray for three days in the dark at
25 °C. The uniformly germinating eight seedlings were
transplanted on a stainless net covering a plastic cup
(100 ml) which contained the test solution. The seedlings
were incubated for ®ve days in the white light
…20 lmol=m2 =s†, and then the shoot and root lengths
were measured.
3. Results
Table 1 shows the e€ect of the WE from the tomato
juice waste on the shoot and root growth of cockscomb
and tomato seedlings. A potent growth-promoting
activity in WE on the growth of the cockscomb was not
found.
To obtain a potent plant growth-promoting substance, the tomato waste was treated with HCl. Table 2
shows the e€ects of the AEs from the tomato juice waste
on the growth of the cockscomb. For the shoot growth
of cockscomb, the growth-promoting activities of the
AEs were higher than that of the WE (Tables 1 and 2).
The maximum activity of the shoot growth was found at
the 4AE. The promoting activity in the AEs decreased
when the fractions were heated for over 4 h. For the root
growth of cockscomb, the growth-promoting activity
was not obtained from the AEs.
To con®rm whether or not the activity of 4AE is related to the neutralization salt and other organic substance(s), inorganic elements (B, Na, Mg, Al, P, K, Ca,
Fe, Ni, Cu and Zn) in the 4AE were determined by an
ICP emission spectrochemical analysis and the e€ect of
the largest quantity of each determined substance was
tested. The largest inorganic element quantity was Na;
330 ppm in a 1000 ppm solution of 4AE. The e€ect of
NaCl was only 123% shoot growth at a concentration of
1000 ppm, the most e€ective concentration. The contents of other determined elements, B, Mg, Al, P, K, Ca,
Fe, Ni, Cu and Zn, were less than 8 ppm, therefore the
contribution of the inorganic elements would be low.
Fig. 1 shows the e€ect of 4AE on the growth of tomato seedlings. Compared with WE (Table 1), the e€ect
on shoot growth increased. When the value of the tomato shoot growth of the control was 100%, the shoot
lengths at the concentration of 500 ppm in the WE and
Table 1
The e€ects of the WE from tomato juice waste on the growth of cockscomb and tomato
Length (% of control)
100 ppm
300 ppm
500 ppm
1000 ppm
Cockscomb
Shoot
Root
109.6 10.2
114.9 6.7
115.3 8.0
103.2 5.7
125.6 7.7
102.3 6.0
123.7 9.5
105.2 4.4
Tomato
Shoot
Root
105.2 12.4
105.3 13.3
112.4 11.4
110.2 10.2
125.3 12.7
103.2 9.9
126.5 13.2
105.2 13.3
Data represent means S.E.
94
T. Suzuki et al. / Bioresource Technology 81 (2002) 91±96
Table 2
The e€ects of the acid extracts from tomato juice waste on the growth of cockscomb
Length (% of control)
Heat time (h)
100 ppm
300 ppm
500 ppm
1000 ppm
2
Shoot
Root
130.8 7.4
97.6 7.6
141.4 3.7
110.6 4.9
166.4 5.3
96.0 8.5
172.7 6.1
97.6 5.8
4
Shoot
Root
135.0 5.2
102.0 6.6
155.8 6.6
99.9 5.9
170.4 10.9
117.9 6.1
200.8 7.6
101.6 5.2
6
Shoot
Root
125.0 7.0
122.5 7.6
130.5 7.1
134.1 4.0
139.0 7.0
130.6 9.5
141.9 5.3
124.3 9.9
8
Shoot
Root
109.5 8.8
113.9 6.7
116.2 8.6
106.3 8.4
130.6 5.8
135.0 10.6
137.5 9.3
126.8 6.4
Data represent means S.E.
Fig. 1. The e€ects of the 4 h acid extract (j-j), NaCl (-) and
glucose (-) on: (A) the shoot (B) root growth of tomato. Data are
mean values, n ˆ 16. Standard error bars are shown when bigger than
symbol.
the 4AE were 125% and 188%, respectively. In particular, the root growth of 4AE at the concentration of 500
ppm was approximately ®vefold to that of the control
growth. When compared with the NaCl e€ect, the
growth-promoting activity was not dependent on the
neutralization salt in the tomato assay. These results
indicated that some plant growth substances were produced from the tomato juice waste by acid hydrolysis
treatment.
To determine the most e€ective substance in 4AE,
500 g of tomato juice waste (wet weight) was heated
with 2.5 l of 0.5 N HCl at 70 °C for 4 h, adjusted to
pH 7.0 with NaOH, and then extracted. After these
treatments, approximately 300 g (dry weight) of
extract was obtained. By the acid treatment, the
weight of tomato waste was reduced by over 60% (wet
weight). The acid extract was fractionated using four
separation steps, that included anion exchange chromatography, precipitation, ultra®ltration, and gel
chromatography. In each separate fraction, the existence of oligosaccharides was recognized, and they
promoted the shoot growth of the cockscomb. From
the gel chromatography analysis, the fraction of the
retention time from 60 to 120 min (16 mg) showed the
highest e€ect on the growth of the cockscomb. The
fraction at the concentration of 1000 ppm showed a
166% promotion on the shoot growth of the cockscomb (data not shown).
The fraction was analyzed using an HPAEC-PAD
method. Fig. 2(A) demonstrates that the fraction was
separated into four parts that included Rt 2.5, 4.8, 7.5,
and 8.4±11.0 peaks. The Rt 2.5, 4.8, 7.5 peaks had
strong response in the PAD analysis; however, the solutions of the fractions from these peaks did not react
using the phenol±H2 SO4 and m-hydroxybiphenyl
methods (Fig. 2(B)). On the other, the Rt 8.4±11.0
peaks reacted strongly during these methods (Fig. 2(B)).
The sum of the contents in the Rt 8.4±11.0 peaks was
almost the weight of the injected sample (approximately
over 98%), therefore, the activity of the most e€ective
fraction depended on the substances of the 8.4±11.0
peaks. From the results of the neutral sugar and uronic
acid analyses, the components of these substances
consisted entirely uronic acids (Fig. 2(B)). The arrows in
Fig. 2(A) demonstrate the Rt of the oligogalacturonic
acids (DP 3±7) under this condition. This suggested that
the DP of the substances would be 6±12. The sugar
components of the fraction were determined by the
ABEE derivative method. The highest value content
was GalUA (approximately 90%). The minor sugars
were Gal, Glc, GlcUA and two unknown substances
were recognized.
T. Suzuki et al. / Bioresource Technology 81 (2002) 91±96
Fig. 2. (A) The HPAEC-PAD chromatogram of the most e€ective
fraction. 500 ll of 0.1% sample solution was injected. Arrows indicate
Rt of oligogalacturonic acids (DP 3±7). (B) The uronic acid (-) and
neutral sugar (-) content of each fraction.
These results demonstrate that the most e€ective
substance in 4AE was an oligogalacturonic acid (approximately DP 6±12).
4. Discussion
We attempted to produce some plant growth substances from tomato juice waste. A potent growth-promoting activity was shown in the acid extract from
tomato waste. The growth-promoting activities for
cockscomb and tomato seedlings of 4AE were higher
than that of WE (Tables 1 and 2). Especially, the percent
of tomato root growth increased ®vefold using 4AE. It
suggests that some substances in the 4AE fraction would
become a good plant growth regulator for tomato culturing. In this study, hydrochloric acid and sodium hydroxide were used for the acid extract and
95
neutralization, respectively. If the acid and bases were
changed to other chemicals, more e€ective inorganic
substances might be produced and the whole materials
become more e€ective fertilizers which contain plant
growth substances.
4AE was investigated and it was shown that the most
e€ective fraction contained acid oligosaccharides (approximately DP 6±12) (Fig. 2). It has been reported that
plant cell fragments promoted plant growth (Adachi
et al., 1988; Fry et al., 1993; Yonemoto et al., 1993;
Natsume et al., 1994; Yamaguchi et al., 1996). As one of
the alleopathic factors, a novel growth-promoting substance was isolated from the mucilage of germinated
cress seeds, and identi®ed as sodium 2-O-rhamnopyranosyl-4-deoxy-threo-hex-4-enopyranosiduronate (lepidimoide) (Hasegawa et al., 1992; Yamada et al., 1995;
Yamada et al., 1996; Yokotani-Tomita et al., 1998).
Lepidimoide promoted the hypocotyl growth of etiolated cockscomb at concentrations higher than 3 mM
and the activity of the substance was 20 or 30 times
higher than that of gibberellic acid. Fry et al. (1993)
reported that lepidimoide might be formed by the
cleavage of a pectic polysaccharide by lyase and endorhamnosidaes. According to Yamaguchi et al. (1996),
oligogalacturonic acids and the decomposition of polygalacturonic acid by pectinase promoted the growth of
lettuce seedlings. Adachi et al. (1988) and Yonemoto
et al. (1993) reported that an alginate lyase-lysate (ALL)
had growth-promoting e€ects on the elongation of
several plants. Natsume et al. (1994) reported that
trisaccharides derived from ALL have root growthpromoting activity in barley.
There are some reports that suggested that plant cell
fragments, which were obtained from enzymatic degradation, promoted the growth of some species of plants.
However, the plant growth oligosaccharides directly
produced from food industrial wastes have not yet been
examined. Using some enzymes is an easy way, however,
it seems to be too expensive to make useful substances
from wastes. This paper is the ®rst report that plant
growth-promoting oligosaccharides could be directly
produced from tomato juice waste by acid extraction.
In this study, we have found potent growth-promoting substances in acid extract from tomato waste. There
are four merits of the acid extract method:
1. plant growth substances, oligogalacturonic acids can
be produced,
2. the method is simple,
3. the method can remove water, decrease the amount
of waste and improve preservation of the waste,
4. the second waste generated by this method might be
used as fuel.
We insist that waste from a food factory should be
reused in the factory. For instance, if the tomato juice
waste were treated with the method in this study, the
acid extract and the second waste would be obtained.
96
T. Suzuki et al. / Bioresource Technology 81 (2002) 91±96
The acid extract might be used for a fertilizer for
tomato farm or house cultivation, and the second
waste from the acid extraction might be used as a fuel
in tomato juice factories. This needs further investigation.
Acknowledgements
The authors are deeply indebted to Professor Dr.
Naoki Sakurai of Hiroshima University for his considerable assistance with the analysis of HPAEC-PAD. The
authors are also grateful to Kagome Co., Ltd. for help
in the determination of the inorganic substances in the
extract from tomato waste.
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