universiti putra malaysia bioconversion of palm kernel cake and its

UNIVERSITI PUTRA MALAYSIA

BIOCONVERSION OF PALM KERNEL CAKE AND ITS EVALUATION AS AN AQUAFEED INGREDIENT

ILUYEMI FLORENCE BUCHI

FP 2003 31


By


Thesis Submitted in Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Faculty of Agriculture Universiti Putra Malaysia

October 2003

DEDICA TED TO

MY HUSBAND

AND

MY SONS

11

111

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirements for the degree of Doctor of Philosophy.


By


April 2003

Chairman: Associate Professor Mohamed Hanafi Musa, Ph.D

Faculty: Agriculture

Palm kernel cake (PKC) is one of the by-products of the oil palm industry. Malaysia

being the world's largest producer of oil palm produces over a million tones of PKC

annually. Traditionally, PKC is used as an ingredient in ruminant feed and its use for

non-ruminants is usually in low amounts due to problems of digestibility. In this

study, an attempt was made to microbially enrich the PKC protein content using:

Trichoderma harzianum, Trichoderma koningii, Trichoderma longibrachiatum,

Aspergillus niger and Sclerotium rolfsii fungi. In the solid-state fermentation (SSF),

effects of inoculum concentrations (1, 2 and 3%), moisture levels (41, 44 and 47%)

and pH levels (3.5, 4.0, 4.5, and 5.0) were evaluated. Protein content of PKC

increased significantly (P�0.05) coupled with a significant reduction in cellulose and

hemicellulose contents by all the fungi used. The highest protein increase of 33%

was obtained using T. longibrachiatum fermented PKC compared with 18% in

unfermented PKC. The effect of moisture content was more critical compared to pH.

Fermentation increased the analysed total amino acids (14 to 25%) and mostly the

unsaturated ones (oleic and linoleic acids). The extracellular enzymes activity

IV

secreted, such as �-D-mannanase, �-mannosidase, a-galactosidase, endoglucanase,

and fllter paper cellulase (Fpase) by hydrolysing of PKC polysaccharides was

evaluated by monitoring the amount of reducing sugar released the crude enzyme

extracts. A wide range of enzyme activities was obtained from the various fungi,

while the amount of reducing sugar released ranged from 0.05 glml for S. rolfsii to

1.05 glml for A. niger. The S. rolfsii and A. niger were good producers of mannan

degrading enzymes when cultured with enriched nutrient medium containing PKC as

the carbon source. The scaled up protein enrichment of PKC using SSF was carried

out using T longibrachiatum in the plastic bag and in a rotating drum bioreactor

made from transparent PVC at 47% moisture level and pH 4.5. The bioreactor

fermented PKC gave a protein (31.78%) value higher than that of plastic bag

fermentation due the difficulty in controlling temperature and insufficient of aeration

of the latter. The formulation of test diets for fish using red tilapia was done by

incorporation of 10 to 40% of fermented PKC in the diets. Feed digestibility as well

as overall growth of fish was evaluated for eight-weeks. Digestibility of diets (53 to

74%) was lower in comparison with reference diet (81%). Fish on test diets also

showed lower body weight gain (53 to lO5%) compared to reference diet ( 1 14%) and

inferior feed conversion ratio (3.0 to 5.3), compared to reference diet (2.9).

However, carcass of fish on test diets had higher phosphorus and calcium content

compared to those on reference diet. In conclusion, PKC is a good carbon source for

the production of cellulose and hemicellulose degrading enzymes. Its protein content

can be increased through fungal fermentation and fish feeds can contain this protein

enriched PKC up to 10% of diet as a partial fish meal and binder replacement.

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi kepeduan untuk ijazah Doktor Falsafah.

BlOPENUKARAN HAMPAS ISIRONG SA WIT DAN PENlLAIANNY A SEBAGAI BAHAN MAKANAN AKUAKULTUR

Oleh

lLUYEMl FLORENCE BUCHl

April 2003

Pengurusi: Profesor Madya Mohamed Hanafi Musa, Ph.D

Fakulti: Pertanian

v

Hampas isirong sawit adalah salah satu hasil sampmgan industri kelapa sawit.

Malaysia merupakan pengeluar kelapa sawit utama dunia dengan menghasilkan lebih

satu juta ton isirong sawit setiap tahun. Secara tradisinya, hampas isirong sawit ini

digunakan sebagai bahan dalam kandungan makanan ruminan dan dimakan dalam

jumlah yang rendah untuk makanan bukan-ruminan kerana masalah penghadaman.

Dalam kajian ini, usaha telah dilakukan bagi memperkayakan kandungan protein

hampas isirong sawit secara mikrob dengan menggunakan: kulat Trichoderma

harzianum, Trichoderma iwningii, Trichoderma longibrachiatum, Aspergillus niger

and Sclerotium rolfsii. Dalam keadaan fermentasi pepejal (SSF), kesan kepekatan

inoculum (1, 2 dan 3%) tahap kelembapan (41, 44 dan 47%) dan tahap pH (3.5, 4.0,

4.5, dan 5.0) telah dinilai. Kandungan protein hampas isirong sawit bertambah

dengan ketaranya (P::;0.05) diikuti dengan pengurangan yang serupa dalam

kandungan selulosa dan hemiselulosa dengan menggunakan kesemua kulat tersebut.

Pertambahan protein yang tertinggi sebanyak 33% telah diperolehi dengan

VI

menggunakan hampas isirong sawit yang difermentasikan dengan T.

longibrachiatum jika dibandingkan dengan 18% dalam isirong sawit yang tidak

difermentasikan. Kesan kandungan kelembapan didapati Icbih kritikal dibandingkan

dengan pH. Fermentasi telah meninggikan jumlah asid amino (14 ke 25%) dan

kebanyakannya yang tidak tepu (asid olik dan linolik). Aktiviti enzim ektraselular

yang dikeluakan, seperti �-D mannanase, �-mannosidase, a-galactosidase,

endoglucanase and Fpase melalui hidrolisis hampas isirong sawit telah dinilai dengan

melihat jum1ah gula terturun yang dikeluarkan dari ekstrak enzim mentah. Berbagai

aktiviti enzim telah didapati daripada pelbagai kulat dengan jUmlah gula terturun

yang dikeluarkan da1am lingkungan 0.05 g1ml untuk S. rolfsii ke 1.05 g1ml untuk A.

niger. S. rolfsii dan A. niger merupakan pengeluar terbaik bagi enzim mannan

apahila dikultur dengan media yang diperkayakan dengan hampas isirong sawit

sebagai sumber karbon. Peningkatan kandungan protein hampas isirong sawit

dengan menggunakan SSF telah dijalankan dengan menggunakan T. longibrachiatum

di dalam karung plastik dan dalam drum bioreaktor yang berputar yang diperbuat

daripada PVC Iutsinar pacta tahap kelembapan 47% dan pH 4.5. Kandungan protein

hampas isirong sawit yang difermentasi di da1am bioreaktor adalah Iebih tinggi jika

dibandingkan dengan fermentasi da1am karung plastik oleh kerana kesukaran untuk

mengawal suhu dan kekurangan pengudaraan. Formulasi ujian pemakanan dengan

menggunakan anak ikan tilapia merah dilakukan dengan memasukan 10 ke 40%

isirong sawit difermentasi dalam pemakanan tersebut. Penghadaman makanan dan

pertumbuhan ikan secara keseluruhannya telah dinilai selama Iapan minggu.

Penghadaman pemakanan (53 ke 74%) adalah rendah jika dibandingkan dengan

bahan makanan rujukan (81 %). Bahan makanan yang diuji juga menunjukkan kadar

Vll

pertambahan berat bedan yang rendah (53 ke 105%) berbanding dengan bahan

makanan rujukan (114%) dan nisbah kadar perubahan pemakanan yang rendah (3.0

ke 5.3) berbanding dengan makanan rujukan (2.9). Walau bagaimanapun, karkas

ikan yang diuji mengandungi unsur fosforus dan kalsium yang tinggi dibandingkan

dengan yang berada dalam ikan yang dirawat dengan bahan makanan rujukan.

Sebagai kesimpulannya, hampas isirong sawit adalah suatu sumber karbon yang baik:

untuk pengeluaran enzim penguraian selulosa dan hemiselulosa. Kandungan

proteinnya boleh ditambah melalui fermentasi kulat dan pemakanan ikan boleh

mengandunyi isirong yang diperkaya sehingga tahap 10% sebagai penggantian

sebahagian daripada makanan ikan dan pengikat.

vm

ACKNOWLEDGEMENTS

I would like to thank the Almighty God for the opportunity and grace to have

accomplished this study.

My sincere thanks and appreciation goes to the Chairman of my supervisory

committee, Associate Professor Dr. Mohamed Hanafi Musa for his patience and

knowledgeable supervision throughout the course of this programme. I also wish to

extend my gratitude to Associate Professor Dr. Mohd. Salleh Kamarudin and Dr.

Radziah Othman for their guidance and invaluable suggestion throughout the study

period.

I wish to also acknowledge the help from some of my colleagues, Mohammed Jalloh,

Osman Haruna, Abdul Samad, Ladan as well as the technical staff of the Faculty of

Agriculture, especially Mrs. Fouzaiah Sulaiman.

My deepest gratitude goes to my husband for his support and understanding, without

which I would not have been able to carry out this study. To Dashe and Chukwuma,

thank you. I would like to thank my Mother, Cecelia Nweke for her spiritual support

and sacrifices without which I would not have been able to attain this academic

degree.

I acknowledge the Faculty of Agriculture, University Putra Malaysia for the premises

and facilities used in this study.

Serdang, Malaysia, April 2003.

I certify that an Examination Committee met on the 6th of August 2003 to conduct the final examination of Iluyemi Florence Buchi on her Doctor of Philosophy thesis entitled "Bioconversion of Palm Kernel Cake and its Evaluation as an Aquafeed Ingredient" in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universisti Pertanian Malaysia (Higher Degree) Regulation 1981. The committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows:

Azizah Hashim, Ph.D.

Professor Department of Land Management Faculty of Agriculture Universiti Putra Malaysia

Mohamed Hanafi Musa, Ph.D.

Associate Professor Department of Land Management Faculty of Agriculture Universiti Putra Malaysia

Radziah Othman, Ph.D.

Department of Land Management Faculty of Agriculture Universiti Putra Malaysia

Mohd. Saleh Kamarudin, Ph.D.

Associate Professor Department of Agricultural Technology Faculty of Agriculture Universiti Putra Malaysia

Mohd. Jaafar Daud, Ph.D.

Pusat Penyelidikan Terkan Institute Penyelidikan dan Kemajuan Pertanian

RAHMAT ALI, Ph.D.

ProfessorlDe uty Dean School of Graduate Studies Universisti Putra Malaysia

Date: 6th August 2003

This thesis submitted to the senate of Universiti Putra Malaysia and has been accepted as fulfillment of the requirement for the degree of Doctor of Philosophy. The

members of the supervisory committee are as follows:

Mohamed Hanafi Musa, Ph.D.

Associate Professor Department of Land Management Faculty of Agriculture Universiti Putra Malaysia (Chairman)

Radziah Othman, Ph.D.

Department of Land Management Faculty of Agriculture Universiti Putra Malaysia (Member)

Mohd. Saleh Kamarudin, Ph.D.

Associate Professor Department of Agricultural Technology Faculty of Agriculture Universiti Putra Malaysia (Member)

AINI IDERIS, Ph.D.

ProfessorlDean School of Graduate Studies Universisti Putra Malaysia


Xl

DECLARATION

I hereby declare that the thesis is based on my original work except for the quotations and the citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions.

ILUYEMl�E BUeHl


TABLE OF CONTENTS

Page

DEDICATION ABSTRACT ABSTRAK ACKNOWLEDGEMENTS APPROVAL SHEETS DECLARATION FORM LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS

CHAPTER

I INTRODUCTION

II LITERA TURE REVIEW 2. 1 Palm kernel cake

2. 1. 1 Source 2. 1.2 Chemical composition 2. 1.3 Uses

2.2 Solid state fermentation 2.2. 1 History 2.2.2 Important procedures in SSF 2.2.3 Moisture and water activity 2.2.4 Temperature and heat exchange 2.2.5 pH 2.2.6 Mass transfer 2.2.7 Aeration 2.2.8 Control of contaminants 2.2.9 Substrate concentration and availability 2.2. 10 Bioreactor selection

2.3 Pretreatments 2.3. 1 Mild alkali treatment 2.3.2 Strong alkali without heat 2.3.3 Hot alkali treatment 2.3.4 Peracetic acid delignification 2.3.5 Dilute acids 2.3.6 Concentrated acids 2.3.7 Use of oxidizing agents

X11

11 ill V

Vill IX Xl

XVI XV11 XIX

1

10 1 2 14

14 15 16 18 20 23 24 25 26 27

29 29 30 30 3 1 3 1 32

X11l

2.3.8 Autoclaving 32 2.3.9 Steam explosion 32 2.3. 10 Acid steam pretreatment 33 2.3. 1 1 Water 33

2.4 Microbial basis of process 33 2.4. 1 Aspergillus 35 2.4.2 Trichoderma 36 2.4.3 Scelrotium rolfsii 37

2.5 Tilapia 2.5. 1 Biology 38 2.5.2 Cultivation 40 2.5.3 Dietary requirements 4 1 2.5.4 Outlook of fish feed production in Malaysia 42

2.6 Summary 43

m GENERAL MATERIALS AND METHODS 3. 1 Chemical analysis 46

3. 1. 1 Determination of moisture and dry matter 46 3. 1.2 Determination of ash 46 3. 1.3 Crude protein 47 3. 1.4 Ether extract 48 3. 1.5 Determination of crude fibre 49 3. 1.6 Determination of acid detergent fibre 50 3. 1.7 Determination of acid detergent lignin 5 1 3. 1.8 Determination of neutral detergent fibre 52 3. 1.9 Determination of mineral 53 3. 1. 10 Determination of gross energy 54 3. 1. 1 1 Determination of amino acids 55 3. 1. 1 1. 1 Acid hydrolysis 55 3. 1. 1 1.2 Drying 56 3. 1. 1 1. 3 Re-drying 56 3. 1. 1 1.4 Derivatization 56 3. 1. 1 1.5 Standard preparation 57 3. 1. 1 1.6 HPLC analysis 57 3. 1. 1 1. 7 Calculation of amino acids 58 3. 1. 12 Feed digestibility 58

IV FUNGAL PROTEIN ENRICHMENT OF PALM KERNEL CAKE UNDER SOLID STATE CONDITIONS: EFFECTS ON DEGRADATION OF CELLULOSE AND HEMICELLULOSE 4.1 Introduction 60 4.2 Materials and methods

4.2. 1 Fungal strains 62 4.2.2 Effect of inoculum concentration on fungal protein

enrichment of palm kernel cake 63

4.3

4.2.3 Effect of moisture level 4.2.4 Effect of using palm kernel cake as the carbon source 4.2.5 Effect of initial pH 4.2.6 Statistical analysis Results 4.3. 1 Composition of palm kernel cake

4.3.2 Effect of inoculum concentration on fungal protein

XlV

64 64 65 65

enrichment of palm kernel cake 66 4.3.3 Effect of moisture content 68 4.3.4 Effect of palm kernel cake as carbon source 7 1 4.3.5 Effect of pH on extracellular protein production 72 4.3.6 Effect of optimum pH and moisture on protein content of

fermented palm kernel cake 74 4.3.7 Changes in hemicellulose and cellulose content of fermented

palm kernel cake 75 4.4 Discussion 76 4.5 Conclusion 79

V EFFECT OF FUNGAL FERMENTATION ON THE FATTY ACID AND AMINO ACID CONTENT OF PALM KERNEL CAKE 5. 1 Introduction 80 5.2 Materials and methods

5.2. 1 Preparation of fatty acid methyl esters 82 5.2.2 Statistical analysis 83

5.3 Results 5.3. 1 Fatty acids content of fermented palm kernel cake 84 5.3.2 Amino acids content of fermented palm kernel cake 87

5.4 Discussion 87 5.5 Conclusion 9 1

VI ENZYMA TIC RELEASE OF REDUCING SUGARS FROM PALM KERNEL CAKE USING FIVE FUNGAL SPP.

6. 1 6.2

6.3

6.4 6.5

Introduction Materials and methods 6.2. 1 Crude enzyme preparation and enzyme activity assay 6.2.2 Enzyme activity assay 6.2.3 Saccharification of palm kernel cake 6.2.4 Statistical analysis Results 6.3. 1 Enzyme activity 6.3.2 Saccharification of palm kernel cake Discussion Conclusion

92

94 94 95 96

96 100 101 102

xv

VII MANNAN DEGRADING ENZYME PRODUCTION BY FUNGI GROWN ON PALM KERNEL CAKE 7.1 Introduction 104 7.2 Materials and methods

7.2. 1 Liquid solid cultivation of palm kernel cake 106 7.2.2 Solid state cultivation condition of palm kernel cake 106 7.2.3 Enzyme activity assay 107 7.2.4 Statistical analysis 107

7.3 Results 7.3. 1 Liquid solid cultivation of fungi using palm kernel cake 1 08 7.3.2 Time course of mannanase production 1 1 1 7.3.3 Solid state cultivation of fungi on palm kernel cake 1 13

7.4 Discussion 1 15 7.5 Conclusion 1 18

vm SCALE-UP SOLID STATE FERMENTATION OF PALM KERNEL CAKE

IX

8. 1 Introduction 1 19 8.2 Materials and methods

8.2. 1 Cultivation in plastic bags 1 20 8.2.2 Bioreactor design and cultivation 1 22 8.2.3 Analytical determinations 1 22

8.3 Results 8.3. 1 Proximate analysis 1 23

8.4 8.5

Discussion Conclusion

PERFORMANCE OF RED TILAPIA FED WITH FERMENTED PALM KERNEL CAKE: A SHORT-TERM FEEDING TRIAL 9. 1 Introduction 9.2 Materials and methods

9.2. 1 Preparation of experimental diets 9.2.2 Feeding trial 9.2.3 Carcass analysis 9.2.4 Digestibility studies 9.2.5 Statistical analysis

9.3 Results 9.3. 1 Growth trial 9.3.2 Carcass analysis 9.3.3 Protein and dry matter digestibility

9.4 Discussion 9.5 Conclusion

1 24 1 27

1 28

1 29 l30 l33 l33 l34

l34 l35 l35

l37 140

x GENERAL DISCUSSION

REFERENCES APPENDIX VITA

XVI

142

146 1 61 1 63

XVll

LIST OF TABLES

Table Page

2.1 Recommended amount of protein, lipids and fibre in percent on as

fed basis. 42

4.1 Composition of PKC 66

4.2 The effects of sucrose and PKC as the carbon sources for inoculum preparation on the CP content of fermented PKC using SSF 72

4.3 Effects of initial medium pH of 4.5, and PKC as the carbon source on protein content using SSF technique 74

5.1 The gas chromatograph parameters used for fatty acid analysis 83

5.2 Effect of fermentation on the fatty acids content of PKC 85

5.3 Fatty acid composition of palm kernel oil 85

5.4 Effect of fermentation on the amino acids content of PKC 88

8.1 Comparison of analysis results obtained from SSF of PKC in plastic bag and bioreactor with aeration.

9.1 Feed Ingredients and Levels of Incorporation 132

9.2 Proximate analysis of feeds 133

9. 3 Mean weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio and survival 136

9.4 Mean percent protein, lipids, ash, phosphorus, calcium, copper and moisture of whole fish. 137

9.5 Percentage protein digestibility of test diets. 138

xvm

LIST OF FIGURES

Figure Page

2.1 Cross section of the oil palm fruit 1 0

2.2 The external appearance and internal structure of the oil palm 11

2.3 Scanning electron photomicrographs of the fIltering apparatus of Tilapia galilaea G = gill rakers, M = microbranchiospines 39

2.4 Alimentary tracts of Tilapia heudelotii 39

4.1 Effect of inoculum level on the CP content of solid state fermented PKC 67

4.2 Effect of moisture level on the CP content of solid state fermented PKC 69

4.3 Interaction of moisture levels and inoculum concentrations on the protein content of solid state fermented PKC 71

4.4 Effect of pH on the extracellular protein content of liquid inoculum medium 73

4.5 Hemicellulose and cellulose content following treatment with fungi in SSF of PKC 76

5.1 Percentage composition of (a) Saturated fatty acids (b) Unsaturated fatty acids of fermented PKC using several fungi in SSF technique 86

6.1 Activities of (a) J3-D-mannanase, (b) endoglucanase, (c) Fpase, (d) J3-mannosidase and a-galactosidase obtained under the conditions used for medium preparation for protein enrichment 1 00

6.2 Effect of crude enzyme extracts on the concentration of reducing sugars released during LSF of PKC 101

7.1 Activities of (a) J3-D-mannanase, (b) J3-mannosidase and (c) a-galactosidase produced by different fungi after 13 days of growth on PKC using LSF 111

XIX

7.2 Effect of incubation time on mannanase activity produced by different fungi grown on PKC using LSF 113

7.3 Mannan-degrading enzymes activities produced by (a) A. niger and (b) s. rolfsii using SSF 114

7.4 Comparison of mannanase activity under LSF and SSF for A. niger and S. rolfsii 115

8.1 The SSF of PKC with T. logibrachiatum in autoclavable plastic bags

(a) without aeration, and (b) aeration. 122

8.2 Setup for SSF of PKC in a rotating drum-type bioreactor. 124

ADF

ADL

ANOVA

BW

CF

CP

D

DE

DM

EE

FAO

FCR

GC

HPLC

LSD

LSF

NDF

NSP

PER

PKC

PITC

PORLA

LIST OF ABBREVIATIONS

: Acid detergent Fibre

: Acid detergent Lignin

: Analysis of variance

: Body weight

: Crude Fibre

: Crude Protein

: Diet

: Digestible Energy

: Dry matter

: Ether Extract

: Food and Agricultural Organization of the United Nations

: Feed conversion ratio

: Gas Chromatography

: High Pressure Liquid C hromatography

: Least Significant Difference

: Liquid solid fermentation

: Neutral detergent Fibre

: Non-starch polysaccharides

: Protein efficiency ratio

: Palm kernel cake

: Phenyl-isothiocyanate

: Palm Oil Registration and Licensing Authority

xx

PTC

PUFA

SGR

SSF

TL-PKC

UPM

: Phenyl-thiocarbamine

: Polyunsaturated fatty acid

: Specific growth rate

: Solid state fermentation

: Trichoderma longibrachiatum fermented palm kernel cake

: Universiti Putra Malaysia

XXI

1

CHAPTER I

INTRODUCTION

The concept of bioconversion of organic solid substrates into useful products is not

new. It has been used for many centuries, long before the underlying

microbiological, biochemical and bioengineering principles were understood. Thus,

the early developments were based on local traditional practices, rather than on

accurate scientific basis. Recently, a lot of scientific research and developments are

being carried out either to upgrade or optimise traditional technologies or to develop

new ones for maximum utilization of organic solid substrates for the production of

feed, food, fuels and fertilizers. At present, many types of processes are being

carried out on large scale. Examples are indigenous fermented foods (Steinkraus,

1983), mushroom production (Hatch and Finger, 1979), composting (Diaz et al.,

1982), production of fuels, such as methane and ethanol (NRC, 1981), and the

production of certain enzymes (Kim et al. , 1985). Production of microbial biomass

for animal feed has been carried out mainly on pilot scale (Durand and Chereau,

1988).

Lignocellulosic materials are the main organic substrates that are being used for the

production of microbial biomass. This is because most of the organic carbon that is

produced as plant biomass is accumulated in lignocelluloses, which is the main

strucLUral component of plant cell wall. Chemically, lignocelluloses materials are

2

composed of three major components, i.e. extraneous substances, polysaccharides

and lignin (Janes, 1969). Extraneous substances are made up of ash, terpenes, resins

and phenols (Rydholm, 1965; Janes, 1969). The polysaccharide component is

comprised of mainly cellulose, some hemicellulose together with small quantities of

starch, pectin and water-soluble polysaccharides, such as arabinogalactans. Lignin is

essentially a 3-dimensional phenylpropane polymer with phenylpropane units held

together by ether and carbon-carbon bonds. In lignocelluloses materials, the

percentage of lignin can be as high as 29% in conifers and 26% in broad-leaved

species on a dry matter basis (Leonowicz et al., 1988).

Palm kernel cake (PKC) which is a residue obtained from the extraction of palm

kernel oil is an abundant and low-cost organic raw material in Malaysia as well as

other countries where oil palm is cultivated and processed in large scale. Presently,

Malaysia is the largest producer of oil palm. The cultivated area is estimated at

about 2.3 million hectares with production of oil registering 8 million tonnes in 2000

(PORLA, 2001). The PKC production has been increasing correspondingly. For

example, in 1999, 1.2 million tonnes of PKC was produced. This value however has

increased to 1.6 million in the year 2000. The PKC therefore represents an under

utilized residue in Malaysia. The polysaccharides of most lignocelluloses, which are

composed of predominantly cellulose, produce glucose as the major monomer upon

complete hydrolysis. In contrast, polysaccharides of PKC produced mainly mannose

and some quantities of glucose and galactose upon complete hydrolysis. This is

becuuse PKC polysaccharides are composed mainly of hemicelluloses, which are

3

essentially linear mannan, closely bound to small quantities of galactomannan (Daud

and Jarvis 1992).

The complexity of lignocelluloses reduces their nutritional quality for animal

consnmption (Kim, 1981). Microbiological technologies can help upgrade such

lignocelluloses substrates to increase their biological value in animal feeding. In

nature, microorganisms, mainly bacteria and fungi Jive on lignocelluloses.

Therefore, upgrading usually involves the conversion of these lignocelluloses to

microbial biomass by cultivating fungi, yeasts or bacteria on them with or without

pre-treatment of the lignocelluloses substrate (Zadrazil, 1980; Taniguchi et al.,

1982). Solid-state cultivation of microorganisms is the preferred method since it

mimics the conditions that are prevalent under natural conditions. During solid-state

fermentation, microbial growth is carried out on water insoluble substrates in the

absence of free water. This process offers some advantages, such as simpler

technology, use of a more concentrated substrate, low waste water output and

improved product recovery since the solid mass coming out of the bioreactor would

be the [mal product.

Bacteria and yeasts grow on the surface fIlm of these solid substrates much like in

free liquid. Filamentous fungi, however, can grow in the absence of free water,

utilizing the bound water of the substrate (Tengerdy, 1985). Therefore, fungi are the

most efficient decomposers of lignocelluloses. Various species belonging to the

genera Aspergillus, Penicillum, Trichoderma and Fusarium are commonly used. The

fungi most investigated for animal feed are Trichoderma spp. (Tengerdy, 1985),

universiti putra malaysia bioconversion of palm kernel cake and its

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