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Discussion ll

The first question to be answered, as far as the microbial treatment of lignocellulose is concerned, is: What is the aim of the treatment? It is possible to produce biomass, biogas, or ethanol. The emphasis at this conference seemed to be on biomass production, but it must be admitted that some of the methods proposed do not seem very practical. One chemical treatment before inoculation with a lignin-degrading organism was criticized as using an unnecessarily high concentration of sodium hydroxide, a statement that was disputed but without agreement being reached.

Fermentation in submerged cultures was not favoured for use under rural conditions, and a recommendation was made that surface culture, the so called "solid substrate" technology, should receive more attention. It was suggested that this method should be tried under field conditions. There was also a comment that time is being lost in transferring technology to the villages because of the insistence of research workers on perfecting every factor in the laboratory before taking a process into the field. Much of this work may have little relevance to rural situations where it would not be possible to apply the same constraints as in the laboratory. It was also suggested that, in selecting organisms, it would be advisable first to find out from existing published work what is known of their pathogenic or toxic characteristics.

The chemical treatment of straw offers various possibilities. Sodium hydroxide is very effective in increasing the digestibility of straw, and considerable work has been done on its use. However, its cost, the energy needed to make it, and its polluting effect on the environment all render it unsuitable in the long term for straw treatment in developing countries. Initial results from the use of urea are promising, those from calcium hydroxide less so, but a combination of the two would be worth investigating. It was again emphasized that the reagents and processes that might be suitable in industrialized, temperate-zone countries are not necessarily the best in rural areas of the tropical and sub-tropical countries.


Mini-fermentation technology to produce single-cell protein from molasses

Ir Ign. Suharto
National Institute for Chemistry, Indonesian Institute of Sciences, Bandung, Indonesia

Ir S. Redyowati B.
Faculty of Engineering, University of Gadjah Mada, Yogyakarta, Indonesia

Single-cell protein as a possibility for improving the protein supply
Raw materials
Proposed work programme
Approach and methodology
Estimated cost of the programme

Current status and utilization of carbohydrate residues in Indonesia

General objectives
Main agro-industrial by-products
Development strategy


Indonesia is an archipelago of 13,367 islands with a total land area of about 1,907,950 square kilometres. A major problem is how to transport and distribute food commodities from one island to another.

The population of Indonesia in 1978 was about 140 million, and the net population growth rate is about 2.2 per cent per year. About 80 per cent of the population lives in rural areas and represents mostly lowincome groups. Some 70 per cent of the population lives in Java and Madura, which make up only 7 per cent of the total land area. Kalimantan, Sulawesi, and Sumatra make up 28, 10, and 25 per cent of the total land area, respectively, and are used as transmigration areas for people from Java. The intensity of agricultural land use in Java and Madura is about 0.07 hectares per person.

The third five-year development plan (Repelita lll) covers the period 1 April 1979 to 31 March 1984. According to the general pattern of long-term national development, as stated in Repelita lll, the priority of national development is still focused on the agricultural sector. A more intensive agricultural system in Indonesia will bring economic advantages, but it will also increase the problem of food processing, particularly within the rural areas and the new transmigration areas where people still tend to live in traditional ways.


Single-cell protein as a possibility for improving the protein supply

In Repelita lll, the protein supply and demand pattern is a problem because of the population growth rate. This increases the requirement for protein and better-quality foods in general. As a consequence, "better-quality foods" implies increased quantities of animal protein.

On the supply side, plant protein is not sufficient to supply total requirements, although the opening-up of new transmigration areas has been adding to food crop production. One way to improve the supply of animal protein for human consumption is to increase the production of animal feedstuffs.

Animal feed production at present is based on fish waste and plant protein sources, but because of their relatively high cost it is necessary to seek others. The new sources must (a) have a high nutritional value, (b) not be competitive with food for human consumption, (c) be economically feasible, and (d) be locally available.

It is possible to introduce single-cell protein (SCP) for animal feeding. Its production will use renewable resources and waste sources such as molasses. SCP can minimize the use of fish waste, soybean cake, peanut cake, etc. for animal feeds. This has been shown in poultry feeding trials.

Average feed consumption by one bird is 100 9 per day. In 1979, the total number of birds was 7,500, needing a total of 750,000 kg feed per day. About 10 per cent of poultry feed is from fish or soybean cake or rice bran, which means that 27,375,000 kg per year of fish, soybean cake, or rice bran could be saved if these materials were replaced by SCP, as shown in table 1. High-grade protein is supplied by some types of single cell micro-organisms.


Raw materials

TABLE 1. Quantities of Present Sources of Protein in Feeds for Various Animals That Could Be Saved by Partial Replacement with Single-Cell Protein

  SCP in Compound Feed (kg/ton) Replaced Protein Source % of Total Feed Protein Contributed by SCP
    Sourcea Quantity


Broilers 100 SBM 182 36
Laying hens 80 SBM 145 38
Turkeys 50 FM 62 18
Pigs 100 SBM 182 50
Veal calves 50 SMP 114 17
Trout 250 FM 308 44

Source: Or. Dimmling, Unde GmbH, Dortmund, FRG.

a. SBM = soybean meal; FM = fish meal; SMP = skim-milk powder.

Agro-industrial wastes, particularly molasses and sugar syrup, are available in Indonesia. The current status of sugar production in Indonesian factories is increasing not only in quality but also in quantity. In the past ten years, 56 sugar cane factories have processed 12 million tons of cane per year into 1.4 million tons of cane sugar and 480,000 tons of molasses. In Repelita 111, the government has launched a mini-technology for sugar cane factories that are spread throughout such islands as Sumatra, Kalimantan, and Sulawesi.

Three mini-technologies for sugar cane factories have already been set up in Aceh, West Sumatra, and Kalimantan. The capacity of each factory is 2,000 tons per year. The target of this plan is to establish about 200 mini sugar factories. The private sector plans to erect seven mini sugar factories outside Java. One of the aims of the mini sugar factories is to create a model in order to encourage the private sector to erect more factories of a similar kind.

It is clear that the higher the total cane sugar production, the higher the total availability of molasses. The production of SCP from molasses by using mini-fermentation technology is relevant to rural development and particularly to increasing per capita income. Some considerations in the selection of molasses as a raw material are (i) its year-round availability, contributing to the development of mediumand small scale industries throughout Indonesia, (ii) its potential for helping maintain the efforts of lowincome farmers and decreasing unemployment in rural communities, and (iii) the encouragement these factors may be expected to give to an increase in the spontaneous and regular flow of transmigrants from Java to other islands.

The objectives of this project are:


Justification of the Project

Feed is a relatively high-cost item in the production of meat, fresh milk, eggs, and broilers. One way to solve this problem is to develop and implement the use of SCP for animal feeding. SCP can replace some of the usual protein sources in feedstuffs; soybean meal, fish meal, or skim-milk powder will be replaced by SCP with an equivalent amount of protein.

SCPs have some advantages, such as that yeasts can easily be controlled genetically and their protein content is higher than that in conventional feedstuffs. A most important characteristic of these SCPs is their high protein content, ranging from 40 to 80 per cent of their dry weight on a crude protein basis.

The process, which has been in use for several years, is basically an aerobic fermentation, followed by recovery of the cells. The stoichiometry of SCP processes is:


1.68 CH2O + 0.19 NH3 + 0.68 O2 - 10 {CH17O0,5N0,19 ash} cells
+ 0.17 CO2 +1.14 H2O + 80,000 calories


Proposed work programme

The proposed work programme consists of the following.

1. Laboratory research on SCP from molasses to provide a more quantitative basis for future requirements:


2. Establishment of a pilot or prototype plant, provided with all essential production elements including quality control, to facilitate:


Approach and methodology

In preliminary research activities on the production of SCP, the scale of operation should be considered first, as this will be influenced by the capacity of the pilot plant and commercial scale in the future. The end-product of fermentation technology will be mini-fermentation technology, in terms of simple prodcedure, simple equipment, and low cost.

The capacity of commercial scale production is planned to be about 1,000 tons per year, using molasses as a raw material substrate. BY comparison, mini sugar factories in Indonesia were designed for a capacity of 2,000 tons of sugar per year. According to this information, the following is the sequence of capacity at each stage.

  1. The capacity of the commercial plant will be 1,000 tons of SCP per year, 3.3 tons or (3,300 kg) per day.
  2. The capacity of the pilot plant will be 100 tons of SCP per year, or 334 kg per day.
  3. The capacity of laboratory activities related to the scaling-up process will be 34 kg of SCP per day. This is possible by using six fermentors (4- to 8-litre capacity each).

Laboratory Research on SCP from Molasses

In preliminary research on bioconversion of molasses to SCP, some aspects of the necessary conditions for SCP production from molasses must be studied (pH range, temperature, mean molasses content, reproduction time, specific growth rate, cell density, productivity, yield, oxygen uptake, kinetic analysis, heat of fermentation, nutrient solution, essential amino acid content, energy and utilities required, selection of the best strains of micro-organisms, etc.). All of the variables must be correlated with the SCP product so that the data obtained can be used to set up the pilot plant.

On the laboratory scale, 2 per cent molasses is used as a substrate with a nutrient solution added. This substrate is then fermented with Fleischmann's active dry yeast in a special fermentor with a capacity of about 4 to 8 litres; its working capacity is 4 litres. The inoculum used is 20 per cent substrate and the temperature is 30 0.5C. Other parameters will be adjusted from a control panel. Fermentation time is ten hours.

The number of cells per litre and the oxygen absorption rate during fermentation can be calculated. The specific growth rate can be calculated using this equation:

X = X0Ekt where
X = total cells at t hour, k = specific growth rate
X0 = total cells at t
t = fermentation time

At an agitation rate of 325 rpm, the total number of cells will increase exponentially and will attain equilibrium after eight hours of fermentation. At the higher rate of 490 rpm, the total number of cells will attain equilibrium after seven hours of fermentation. This might be the result of the autocatalysis of cells. Further laboratory development will take place after the joint proposal on feed from agricultural and agro-industrial wastes has been approved.


Estimated cost of the programme

Research and development will require a budget for:
- equipment (six fermentors with 4- to 8-litre capacity, laminar

flow cabinet, spray drier, extraction unit, digital analytical

balance, centrifuge, paramagnetic oxygen analyser, digital pH meter, etc.)

- chemicals and supplies 150,000
- salaries 150,000
- miscellaneous 200,000
Total (for three years) US$900,000
The investment required for SCP production with a capacity of 100 tons per year, or 334 kg per day, will be:
- quoted equipment US$450,000
- estimated equipment installation cost 50,000
- piping 50,000
- instrumentation with some automatic controls 75,000
- auxiliaries (e.g., electric and steam power) 75,000
- buildings 200,000
- maintenance 40 000
- utilities 100,000
- engineering and construction fees 50,000
- salaries 120,000
- operation costs 120,000
- contingency 170,000
Total (for three years) US$1,500,000



The demand for and supply of protein are not in balance, nor is the supply adequate for Indonesia's total population of about 140 million (1978), especially when considering the net population growth rate of 2.2 per cent per year and the difficulties of transportation in the archipelago.

To improve the supply of animal protein for human consumption it is necessary to increase the production of animal feedstuffs. SCP from molasses can replace some of the usual protein sources in feedstuffs. The availability of molasses is at least 480,000 tons per year, and this is increasing because mini sugar factories are operating on the islands outside Java. These experiments are to study the optimum conditions of fermentation and to set up a pilot plant and field trials for SCP production. A pilot plant will be set up to process 100 tons per year, the duration of the project will be three years, and the cost of the programmes for research and development and a pilot plant will be US$900,000 and US$1,500,000, respectively. The plant will be located in Bandung.



Anggorodi, R. "Penghematan Bahan Makanan Berprotein Tinggi dengan Ragi Hidro Karbon dalam Ransum Ternak." Jakarta, Indonesia, 1979.

Coursey, D.G. Cassava as Food: Toxicity and Technology. Tropical Products Institute, London, 1973.

"Engineering of Unconventional Protein Production." Chem. Eng. Progress, Symposium Series, 93:65 (1969).

Indonesian Institute of Engineers. Food Policy in Indonesia. 1979.

John, C.K, "Recycling of Agro-industrial Wastes." Science and Technology Seminar, Kuala Lumpur, Malaysia, 1978.

MacLennan, D.G. "Single-Cell Protein." PACE, April 1974, pp. 13-17,

Proceedings of the Second Poultry Science and Industry Seminar. Ciawi, Bogor, Indonesia, 1979.

Rogers, P.L. "Single-Cell Protein from Agricultural and Industrial Waste." Unpublished paper, University of New South Wales, Sydney, Australia.

Vilbrant, F.C. Chemical Engineering: Plant Design. McGraw-Hill Book Company, London, 1959.


Current status and utilization of carbohydrate residues in Indonesia

Ir Ign. Suharto
National Institute for Chemistry, Indonesian Institute of Sciences, Bandung, Indonesia



The third five-year development plan (Repelita lll, 1979-1984) aims to increase the prosperity of the Indonesian people and lay down a firm foundation for future development. It will be necessary to strike a balance between the agricultural and industrial sectors to ensure economic growth and a more equitable distribution of income between rural inhabitants and city dwellers. The tendency for the poor to become poorer and the rich to get richer is one that needs to be redressed in the interests not only of the people themselves but also of national stability.

The economic growth envisaged during Repelita lll is still based on the agricultural and agro-industrial sectors. About 80 per cent of the 140 million population of Indonesia lives in rural areas, and both rural and city dwellers depend on agriculture for their incomes. But economic growth alone is not the final solution: it must be accompanied by parallel social development. There are important differences in social, political, and cultural influences between rural and city areas, some of which are as follows:

Rural areas

City areas

- lack of science and technology

advanced science and technology

- lack of trained management

no lack of trained management

- adequate natural resources

no natural resources

- protein-calorie malnutrition (PCM)

low incidence of PCM

- plentiful land area

no land area

- adequate manpower

adequate scientific manpower

- little political power

strong political power

Commodity trading is mainly in the hands of city people. The rural inhabitants tend to preserve their traditional way of life and remain in the low-income group, many existing below the poverty line. One way of improving their standard of living is to convert their farm residues into more valuable materials for which there is a use and a demand. In effect, this means increasing the value of residues as animal feeds.

Java comprises only 7 per cent of the total land surface but supports 88 million 163 per cent) of the 140 million people in Indonesia, with a consequent pressure on the land available for agriculture. On the other hand, outside Java the population density is comparatively low and agricultural land is plentiful. It should therefore be feasible to increase production to satisfy the demand for both food for people and animal feed.


General objectives

Many Indonesian farmers have only small agricultural holdings. To increase their incomes they will have to make greater use of crop residues to increase the quantity and quality of animal production. Residues occur at all stages of production, storage, and marketing. These are often wasted or used inefficiently. In either case, their potential value as animal feed is not fully realized.

As well as the effect on farmers' incomes of locally produced animal feed material, an increase in domestic feed production is important in other respects. These are:

However, to obtain these advantages other factors must be taken into account, such as the availability and continuity of supply of the various types of residues and the cost of converting them into better-quality feed materials.

In summary, therefore, the general objectives of projects for increasing the use of agricultural residues are to:


Main agro-industrial by-products

Most agro-industrial by-products are derived from oil palm, tapioca, and sugar cane production. The oil palm industry produces about 270,000 tons of palm oil each year. The by-products include about 1 million tons of liquid effluents, 270,000 tons of empty bunches, 100,000 tons of pericarp fibre, 160,000 tons of shells, and 80,000 tons of palm kernel cake. The cake is used in formulated animal feeds. The palm oil sludge may have a potential use in animal feed.

Over 110 million tons of tapioca meal are produced annually, but only a small amount is available for animal feeding. The sugar cane industry produces 4 million tons of bagasse, 400,000 tons of press mud, and the same amount of molasses. The latter can be used as such in animal feeds or form the substrate for single-cell protein manufacture.

Other agro-industrial residues include rice bran, fodder yeast, coconut press cake, sago meal and waste, soy sauce, soybean curd, and dairy plant wastes. All of these have a use, or a potential for use, in animal feeds. However, more research is needed to evaluate the nutritional characteristics of these materials and their suitability for different types of livestock. Other factors that require investigation are any possible toxicological properties and the effects of processing and handling on bacterial and mycotoxin contamination.

The total feed requirement of livestock in Indonesia, according to Nell and Rollinson, is:

The percentages of these required in Java are 52.6, 38.0, and 55.1, respectively.


Development strategy

As has been stated earlier, the main objective is to become, as nearly as possible, self-sufficient in animal feed production by making better use of the organic residues that are available.

Small-scale fermentation processes have been practiced for some years in Indonesia and are generally known to the farmers. When successful they may have advantages over chemical processes because they need little capital investment to establish and maintain them. For these reasons it may be better to place more emphasis on the development of biological rather than chemical treatment of residues.

The application of fermentation technology would be aimed at preserving feed from spoilage and increasing its nutritional value. This, in turn, would require research and training in biotechnology and in the nutritional and toxicological evaluation of these products.

Whereas this aspect would be the responsibility of institutes or university departments competent to undertake the work, the technology of producing the feed materials would have to be capable of application at the rural level.

Ideally, the whole system of the development of suitable technology, its transfer to rural areas, and the evaluation and application of the resulting feed materials, should be contained within the national policy for development. To achieve this, planning for the future will need to provide the following for the agricultural sector:



The third five-year plan (Repelita lll) is intended to increase the general prosperity of Indonesia and to ensure a more equitable distribution of the national income. A major factor in this will be development of the agricultural sector, particularly in the area of using organic residues for animal feeding more effectively.

Both biological and chemical processes will be developed for this purpose. The nutritional and, where necessary, the toxicological characteristics of products resulting from these processes must be evaluated.

The processes themselves must be capable of application in rural areas on either a community or individual farm scale.

These developments and the facilities needed to carry them out should be seen in the general context of national development in which a balance is required in technical, social, economic, and political influence between city and rural areas.

An interdisciplinary approach to the problems is necessary, as is co-operation with both national and international scientific bodies,