Utilisation of rural wastes for algal biomass production with Scenedesmus Acutus and Spirulina Platensis in India

qgricultural Wastes4 (1982) 117 130

U T I L I S A T I O N OF R U R A L WASTES F O R A L G A L B I O M A S S P R O D U C T I O N WITH S C E N E D E S M U S A C U T U S A N D SPIR ULINA PLA TENSIS IN I N D I A *

L. V. VFNKATARAMAN,K. MADHAVI DEVl, M. MAHADEVASWAMY ~,~ A. A. MOHAMMED KUNHI

Central Food Technologieal Research Institute, Mysore 570 013, India

A BS'FRA C T

,4 technology ,[or the production oJ the green alga, Scenedesmus acutus, and blue green alga, Spirulina platensis, in clean water has been det;eloped at out" Institute to suit Indian conditions. Experience gained on algal production technology in India indicates the seopejor applying this at the rural lereljbr use in the production ql animalJeed. Spirulina is the most promising alga in t'iew of i t s amenabili O' to low lerel technology. Nutrient input to the euhures is one oj the expensive steps. It i~s shown that agricultural and domestic' wastes can be eJ]~cticely reeycled Jor algal biomass production by replacing, at least partly, the nutrient inputs. Urine and honemeal reduce the inputs oJnitrate, calcium and phosphate salts into the cuhure medium. Sheep's blood has a growth promoting eJJect on algal cultures and a good potentialJor application. Carbon dioxide enriched air ~'aerobic biogas'~produced by composting cow dung, can be used as a carbon sourcejor algal cuhication. Seceral experiments carried out in India indicate the possibility q[deceloping an integrated algal production system in rural areas by means oj which wastes can be eJ]ectit:ely recycled. The use q/algae in poultry and fish jeeds is a distinct possibility jor the /uture.

1NTROI)UCT1ON

Waste disposal and pollution problems are less acute in India than in many developed countries (Table 1). This is primarily due to the conventional practice of recycling agricultural, domestic and animal refuse in one way or another. Many of * A part of the data in this paper was presented at the IDRC Workshop on High-Rate Algal Ponds held in Singapore, 27 29 February, 1980.

117 qgrieuhural Wastes 0141-4607/820004-0117502.75 ( Applied Science Publishers ktd, England. 1982 Printed in Great Britain

118

L. V. V E N K A T A R A M A N ETAL.

TABLE 1 GARBAGE PRODUCTION IN INDIA COMPARED WITH THE USA

Country

India USA

Population in millions

Amount of refuse per head per year in kg

661 230

90.8 818.1

Content

90 % b i o d e g r a d a b l e m a t e r i a l 10 °Jo b i o d e g r a d a b l e m a t e r i a l

S o u r c e : T a y l o r et al. (1971).

the methods of waste disposal are neither the best nor the most efficient ways of utilising such wastes. With the increasing industrialisation of India it can be anticipated that more efficient methods of waste disposal and recycling should be sought. Algal biomass productivity is to be viewed in this context. Algae have been considered as a potential unconventional protein source for use in feed and food which has received world-wide attention (Lipinski & kitchfield, 1974; Waslien, 1975; Venkataraman & Ramanathan, 1978: Soeder, 1980). The Central Food Technological Research Institute (CFTRI), Mysore, India, has standardised the method of cultivating the green alga, Scenedesmus acutus, and the blue-green alga, Spirulina platensis, in clean water. Algal production technology at CFTRI was originally initiated under an Indo German collaboration (Becker & Venkataraman, 1976). There has been a shift in the research and development efforts in India subsequent to the realisation that algae can be used as feed instead of the food protein originally contemplated (Venkataraman, 1978; Venkataraman et al., 1978; Seshadri & Sebastian Thomas, 1979). This provides greater flexibility to simplify the cultivation and processing procedures which are otherwise energy and capital intensive. Indian experience on algal production indicates the possibility of the application of this knowledge at a rural level rather than on a semi-commercial or commercial scale. It is possible to develop integrated algal production systems in which rural agricultural wastes can be profitably utilised. Spirulina is the most promising alga for rural application (Venkataraman et al., 1978). However, as the chemical nutrient inputs are rather high, it is imperative to substitute with rural wastes wherever possible. Bonemeal is a good source of phosphate and calcium salts. Steamed bonemeal is superior to mineral phosphates and also contains nitrogen (Sastri, 1957). The potential supply of bones in India is estimated to be 1 million tons annually. Of this only 4000 to 5000 tons are used for fertiliser manufacture (Sastri, 1957). There is good scope for the use of bonemeal to supply calcium and phosphates in algal cultures. Urine is an important waste product of both human beings and animals. The volume of urine produced by man on average is about 1 to 1.2 litres a day. This contains 13-2 g of total nitrogen in normal conditions (West et al., 1966). In India,

RURAL

WASTES FOR ALGAL

PRODUCTION

l 19

which is predominantly an agricultural country where cattle are employed for agricultural operations, there is a great potential for using cow's urine (Lawlor, 1974). Blood from slaughterhouses, where cattle and sheep are processed for meat, is seldom used in India. Several preliminary studies using this waste blood, both at this Institute (Venkataraman, 1978) and at Auroville Centre, Pondicherry, India, have given encouraging results on the utilisation of this waste blood for algal growth. No less than 1200 million tons of wet cow dung are produced every year in India (Biswas, 1976 77). The dung production from the animal population is shown in Table 2. Most of it is presently used as fuel in villages, although this is not an efficient TABLE 2 POTENTIALITY OF ANIMAL POPULATION AND AMOUNT OF DUNG PRODUCEI) 1N INDIA a

Animal

Horses Cattle Buffaloes Pig Sheep Goat

Population in million

Amount o[ dung (million tons per )'ear) (wet weight)

9.9 181.0 61.0 8.8 40-4 70.7

930b 1200 1800 182b 165b 150b

a FAO Production Yearbook (1978), Vol. 32.

b Computed approximations.

way of utilising it. In the past 6 or 7 years there has been great interest in India in using cow dung for the production of biogas which can serve as a fuel. There appear to be two distinct possibilities of using cow dung for algal production. First, the biogas effluent drained out of biogas plants designed for biofuels (called ' G o b a r gas plants" in India) can be added to the algal cultures at suitable levels. The other possibility is to use the dung for producing carbon dioxide enriched air ('aerobic biogas') by aerobically composting cow dung and using the evolved gas as the carbon source in algal cultures. This is an interesting approach which merits serious consideration. This paper reports the findings of several experiments carried out at this Institute using rural wastes for algal production. METHODS

Technology o f algal biomass production in clean water

The salient conditions of the technology of fresh water cultivation and processing of the green alga, Scenedesmus acutus, and blue-green alga, Spirulinaplatensis, have been summarised in Table 3 and are also shown in Figs 1 and 2.

120

L. V. VENKATARAMAN ET AL. Stock Culture on agar slant

Inoculum in ~-Thermostat/

Direct Sunlight

II\

Glasscarboys~ II~ /

/Formula IV ~(Car ban s o u r c e :

CO2°ra¢r°blcbi°gas)

I Outdoor k Culture basins pHTtoB ]

I

Atga¢ powder q

Steam heated drum d r y i n g J

l

Separation by Centrifugatlon f a c t u a t i o n with chitosan

or

I Efflu¢n(~

Poultry or Fish f¢ed

Fig. 1.

Cultivation and processing of Scenedesmus acutus at CFTRI, Mysore, India.

Scenedesmus was cultivated using 'Formula IV' (Table 4) nutrient medium and carbon dioxide gas as the carbon source. Harvesting was achieved by centrifugation or using the cationic polymer, chitosan (Nigam et al., 1980). The algal slurry was dried on a drum drier. The processing technology was adopted from Dortmund, West Germany (Soeder & Pabst, 1975). Spirulina was cultured in clean water with 'CFTRI Mix' (Table 4) as the nutrient source which also contained bicarbonate to serve as the carbon source. Harvesting was carried out by means of a gravity deck filter and drying in sunlight after spreading the slurry on plastic sheets. Other details of the production technology have already been published (Venkataraman et al., 1977; Rajasekaran et al., 1980). Only details of the present experiments are given below. Stock culture on agar slant

Inoculum in Sunlight glass carboys (Thatched roof to cut light ~ntcnslly)

CFTRI Mix. //~Carbon source: J "Bicarbonate or

L o.oo- 1 cultur¢ b a s i n s pH 8.5 to 10-5

Algal = f|akcs

l

Poultry or F i s h feed

Fig. 2.

Sundrying/ Ie crossflow drying

L --,,oo 1 on Gravitational Deck filter

LEffluent

Cultivation and processing of Spirulina platensis at CFTRI, Mysore, India.

RURAL WASTES FOR ALGAL PRODUCTION

121

TABLE 3 C U L T I V A T I O N A N D P R O C E S S I N G OF ALGAE IN CLEAN W A T E R AT CFTRI, MYSORE, I N D I A

Parameters

Spirulina platensis

Stock Nutrients Inoculum

On 2 % agar + nutrients CFTRI Mix" In glass carboys

Outdoor tanks

PVC/cement or pits lined with plastic sheets 240 m 2 Hand brushing Coconut frond shading to cut light intensity Bicarbonate 8"5 10.5 (self adjusting) 6 8 days Gravity filtration Sun drying 8 12

Area cultivated Agitation Light Carbon source pH Retention time in tanks Harvesting Drying Yield(gm 2day 1)

Scenedesmus acutus On 2 % agar + nutrients Formula IV ~ In thermostats or in glass carboys PVC/cement 220 m 2

Motor driven paddle wheels Direct sunlight Carbon dioxide 7 8 5-6 days Centrifugation Drum drying 15 20

" Refer to Table 4.

R a i s i n g oJ the inocula I n o c u l a o f a l g a e w e r e r a i s e d in glass c a r b o y s in c l e a n w a t e r w i t h t h e r e s p e c t i v e n u t r i e n t s ( T a b l e 4). F o r Spirulina, t h e c u l t u r e s w e r e s t i r r e d f o r a p e r i o d o f 15 t o 20 m i n a d a y a n d g r o w n in t h e s h a d e w i t h a n o p t i m u m l i g h t i n t e n s i t y o f 30 t o 35 kllux. T h e p H o f t h e m e d i u m w a s a l l o w e d to s e l f - a d j u s t a n d w a s b e t w e e n 8.5 a n d 10.5. F o r S c e n e d e s m u s c u l t u r e s , a i r w a s b u b b l e d a t t h e r a t e o f 4 0 0 t o 500 m l a m i n u t e p e r 1000 litres, a l o n g w i t h c a r b o n d i o x i d e f r o m g a s c y l i n d e r s . T h e p H w a s m a i n t a i n e d b e t w e e n 7 a n d 8. T h e i n o c u l a t h u s r a i s e d w e r e u s e d in o u t d o o r c u l t i v a t i o n s t u d i e s .

TABLE 4 C O M P O S I T I O N OF N U T R I E N T MIX USED AT CFTR1

Scenedesmus Nutrient Urea K2CO 3

NaaPO 4 NaCI (crude salt)" (NH,d2SO 4 MgSO 4 FeSO 4

(Formula IV) Amount (mg litre 1) 100 25 25 25 20 10 2

Carbon source: Carbon dioxide at 401~ 500 ml per min per 1000 litres

Spirulina Nutrient NaNO 3 KzSO, , K2HPO 4 MgSO 4 CaC12 FeSO 4 NaC1 (crude salt)"

('CFTRI Mix') Amount (g litre 1) 2.5 l'0 0.5 0.2 0-04 0-01 1-0

Carbon source: b

NaHCO 3

a Crude sea salt to supply an undefined amount of micronutrients. b Normal NaHCO 3 levels 16 g litre-1 in Zarrouk's medium.

8"0

122

L . V . VENKATARAMAN E T A L .

Outdoor cultivation The algae were cultivated in outdoor basins, using clean water, under the culture conditions detailed in Table 3. The growth of the cultures was monitored by taking optical density (OD) measurements at 560 nm. Dry weight determinations of algal biomass were made by centrifuging the algal cells at known OD and then drying the wet slurry to constant weight in an oven. A standard graph was prepared relating OD measurements to dry weight of the algae (Venkataraman et al., 1977). After the optimal growth period the algal biomass was harvested and dried as detailed in Table 3.

Utilisation of wastes in algal cultures In all the experiments carried out, rural wastes--bonemeal, urine, blood, biogas effluent and aerobic biogas--were used as follows. (The types of wastes and the levels used are summarised in Table 5). Bonemeal: Spirulina was grown with CFTRI Mix with the substitution of bonemeal at the 2 to 3 ~o level as a complete replacement of calcium and phosphate salts. Bonemeal was not added directly into the medium but was suspended in a nylon mesh in the cultures. Urine." Human urine at the 1 ~o level was used in Spirulina cultures grown with CFTRI Mix but with the complete elimination of N a N O 3. Biogas effluent." The residue left after anaerobic biogas production from biogas plants is here termed 'biogas effluent'. Spirulina was grown on biogas effluent at the 3 ~ and 5 ~o levels. In these experiments CFTRI Mix was supplied at 50 ~,, of normal levels with the biogas effluent. Blood: Fresh sheep's blood obtained from a slaughterhouse was used in Scenedesmus cultures grown on 'Formula IV'. No chemical nutrients of Formula IV were substituted. The addition of blood was in order to study the overall chelating or other beneficial effects on the cultures grown on normal nutrient media, by comparison with preliminary cultures. Blood was added at the 0.1, 0.3, 0.5 and 1-0 ~o levels to the outdoor algal cultures.

Production of carbon dioxide enriched air ('aerobic biogas') from composting of cow dung Carbon dioxide is an important carbon source for algal cultures. The concentration of the gas in air is too low (0.03 ~o) and hence is a limiting factor for the photosynthetic process. Experiments as described below were attempted to produce carbon dioxide enriched air from the aerobic composting of cow dung for use in algal cultures. This was intended to replace the supply of CO 2 from gas cylinders. A series of glass desiccators were used in laboratory trials. One kilogramme of fresh cow dung was kept in each desiccator. A thin stream of air was continuously passed through these desiccators. As a result of aerobic composting, carbon dioxide is released and carbon dioxide-enriched air ('aerobic biogas') is thus obtained. The

Animals

Sheep

Residue from biogas plant Cow dung

Bonemeal

Blood

Biogas effluent 3-5 30~400ml min- 1

0.1 1.0

3.0

1.0

Level used (%)

10 5 10

500

10

500

Volume of culture used (litres)

Function

Replacement of sodium nitrate Replacement of phosphorous and calcium Growth promotion and chelating effect Replacement of 50 %, standard nutrient mix As carbon source

Fresh cow dung mixed with actively degrading compost produces 3 4 % C O 2 enriched air.

Aerobic biogas ~

Human

Source

Urine

Type of waste

TABLE 5 RURAL WASTES USED IN ALGAL CULTURES AT C F T R I

Spirulina Scenedesmus/Spirulina

Scenedesmus

Spirulina

Spirulina

Algal culture in which used

Z

,..-I

©

©

7o

70

124

L.V.

VENKATARAMAN

ETAL.

amount of carbon dioxide produced was determined by bubbling the biogas through a known concentration of Ba(OH)2 and then titrating as in earlier experiments (Mahadevaswamy, 1980). The aerobic biogas was passed through algal cultures in glass carboys, Several laboratory experiments on both the algae were carried out using 5 to 101itres of algal cultures each time. Different composting conditions were used in an effort to obtain greater production of carbon dioxide, as shown in Table 6. TABLE 6 CARBON DIOXIDE PRODUCTION FOR ALGAL CULTIVATION BY AEROBIC FERMENTATION OF COW DUNG a

Material for COz Production Fresh cow dung Fresh cow dung + 1~o urea Fresh cow dung + 1~o (NH,,)2SO4 Partially composted cow dung + green straw (10:1) Advanced stage of compostingcow dung + green straw (10:1)

mg CO2 per kg per h 18'0 (15"4-20"0) 20"0 (11.0-20.0) 15-0 (14-2-16.2) 58-5 (34.1 78.4) 140-0 (130-150)

Amounts tested--I kg. Values in parentheses indicate the range. Average value is a mean of three independent observations.

RESULTS

Algal growth The growth rate of Scenedesmus was higher than that of Spirulina, giving a growth period of 5 to 6 days for Scenedesmus and 6 to 8 days for Spirulina before harvesting. A yield of 60 to 70 mg of algae per 100 ml (dry weight) for Scenedesmus in a growth period of 6 days was obtained using the standard nutrient mix (Formula IV) and carbon dioxide as the carbon source. With Spirulina, the yield was about 50 to 60 mg per 100 ml in 8 days using the ' C F T R I Mix' containing bicarbonate as the carbon source under the growth conditions detailed in Table 3. Bonemeal Ten- to fifteen-litre cultures were raised outdoors, using bonemeal, in carboys as described earlier. The growth rate of Spirulina supplied with bonemeal as a replacement for calcium and phosphate salts is shown in Fig. 3. The initial pH was 9-0 and in six days the pH was shifted to 9.8. Three per cent of bonemeal gave a better growth rate than 2 ~ of bonemeal and there were no nutrient deficiency symptoms; hence the amount added appears to be adequate to replace calcium and phosphate salts completely.

R U R A L WASTES FOR A L G A L P R O D U C T I O N

125

A

~'~o 3"

<2o /

I 4

2 Growth

I 5

1 6

period (days)

Fig. 3. Growth of Spirulinaplatensis with bonemeal, 10litre cultures grownoutdoors, x, Control: ©, 2 % bonemeal: A, 3 % bonemeal.

Human urine Human urine has been successfully used outdoors at a 1% level as a sole source of nitrogen, replacing sodium nitrate which is normally supplied at 2.5 g litre 1 for Spirulina cultures. A yield of 8 to 10g m 2 day-1 can be obtained, as shown in Fig. 4. Similar results were also obtained using cow's urine. No significant difference was found between the experiments with human urine and those with cow's urine.

o

o

120

"~ I0C >,

x Controt A 1o/, H u m a n u r ; n ¢ 0 0.5°1o H u m a n u r ; n ¢

~40 ~

20 I

I

i

I

I

2

3

4

5

6

Growth

p¢r;od (days)

Fig. 4. Growth of Spirulina platensis with human urine, outdoors.

Biogas eJfluent Ten litres of Spirulina culture were raised in glass carboys using biogas effluent. A deep brown colour was imparted to the cultures by the biogas effluent, making optical density measurements nearly impossible. However the cultures grew well, as evidenced by the floating biomass of Spirulina after 6 to 8 days which was harvested by means of the usual procedure. It is possible to use the biogas effluent to replace at least 50 % of the standard nutrient mix for Spirulina.

126

L. V. V E N K A T A R A M A N E T A L .

& ®

160 140 O o

~ x

120

Control 0.1 ml Blood 0.3 ml 0,5 ml " 1.0 ml Blood

/ / / / /

x

x

~I00 80

g 40 9 <

20 0

1

2 3 4 Growth period ( d o y s )

5

Fig. 5. Sheep's blood concentration (ml per 100 ml) versus growth of Scenedesmus acutus. Blood

Whole sheep's blood increased the growth of cultures considerably, as can be seen in Fig. 5. Increased c o n c e n t r a t i o n of b l o o d induced a c o r r e s p o n d i n g increase in the growth of algae in a 5-day growth period up to a 1 7o level of blood. It is n o t desirable to add blood b e y o n d this level in view of c o n t a m i n a t i o n or other p r o b l e m s that m a y be i n t r o d u c e d into the culture. The chelating effect of blood on algal cells is very evident. It is not possible to attribute this to any one fraction or c o n s t i t u e n t of 600' 55O 5O0 450 "~ 400 -90 E

b35o "0

gso

300 (3"

_~-7o

250

:"60

~200

~50

150

E40

IO0

0

9< 3 0

50

2O 1

2

3 4 5 6 7 Growth pcriod~DQys

8

9

Fig. 6. Growth of Scenedesmus acutus culture in glass carboys (5 litre) with air and biogas, air only. Q, 'Biogas' _~500 ml min - 1; O, atmospheric air ~ 500 ml min- 1.

__

!

2

3 Growth

4 5 pcrlod (doys)

I

,

6

Fig. 7. Growth of Spirulina platensis with aerobic biogas, 10 litre cultures grown outdoors. ×, Control; A, compost gas.

RURAL WASTES FOR ALGAL PRODUCTION

127

blood, but to the overall effect. Details of these effects have been reported in the other studies mentioned in the Introduction.

"Aerobic biogas' as a carbon source Scenedesmus and Spirulina cultures were raised in 5-1itre and 10-1itre glass carboys with their respective nutrient media (Table 4), eliminating the carbon sources, carbon dioxide and sodium bicarbonate. Carbon dioxide-enriched air from composted cow dung was passed to the cultures as described in the section above headed 'Methods'. Maximum carbon dioxide (up to 140 mg of CO 2 per kilogramme of fresh cow dung an hour) was obtained by mixing fresh cow dung with actively decomposing compost. The addition of urea or a m m o n i u m sulphate to the fresh cow dung did not improve carbon dioxide production. The cultures grown with this "aerobic biogas' gave a growth rate and consequently a y i e l d - c o m p a r a b l e with those grown on other carbon sources. The details of the growth patterns can be seen in Figs 6 and 7.

DISC USSION

The addition to algal cultures of chemical nutrients and the supply of a carbon source contribute a major part of the cost of algal production. This is all the more crucial tbr Spirulina since nutrient inputs are fairly high compared with those;of Scenedesmus. Venkataraman & Nigam (1980), whilst working on the cost computations of Spirulina, have calculated that chemical nutrient inputs may contribute nearly 48 04, of the Spirulina cost. It has been shown by others in India that chemicals worth Rs.9/- (US$1.20) may be needed in the medium to produce 1 kg of dried Spirulina (Seshadri & Sebastian Thomas, 1979). Mohn & Soeder (1978) attributed about 30 35'~, expenditure on the chemicals for the medium and carbon source whilst working on the economics of Scenedesmus production. Such high costs are prohibitive even if food-trade algae are to be produced. Since algae are considered as animal feed, it is imperative to reduce the cost of the product to the barest minimum. It will be necessary to bring down the cost of algae to that of soya protein in western countries or of ground nut protein (peanut protein) in the Indian context, if not lower. These two oil seeds are also upgraded for human consumption. Algae can possibly replace these oil seeds which are presently used in feed. The production of CO 2 enriched air, here termed 'aerobic biogas' is distinct from the biogas produced by the anaerobic process which contains high amounts of methane. The idea of C O 2 enriched air from cow dung for use as a carbon source appears to be unique and promising. There is no information available in the published literature on this. Encouraged by the results of the laboratory trials discussed earlier, a large chamber was built with cement mortar (termed a "rural

128

L. V. VENKATARAMAN E T A L .

fermenter'), with a volume of 0.5 m 3 which can hold about 1000 kg of cow dung (Fig. 8). The fermenter is charged with fresh cow dung mixed with about 10 ~,, of actively decomposing compost. It is possible to get a continuous supply of CO 2 enriched air which can support algal growth as the sole carbon source. It is necessary to discharge at least half of the composted dung and replace it with an equal amount of fresh cow dung every 8-10 days in order to keep up the CO 2 concentration. The methane content of this gas is negligible. It is necessary to make this fermenter airtight so that the gas coming out can be transferred and bubbled into the algal cultures using either a vacuum pump or a water pump. The system is still under trial and more details of the technical aspects of its utilisation have yet to be worked out to make it a viable model. In several developed countries, the dramatic increases in 'bioindustries' which rear cattle and poultry have led to serious problems of waste disposal (Groenewig et al., 1978; Lee & Dodd, 1980). The amount of manure produced exceeds the limits of utilisation in fields. The piles of manure produced pose problems of contamination and pollution. Efforts are in progress in several countries to find acceptable processes for disposal (Oswald & Gotass, 1957; Shelef, 1979). The use of algal systems has shown promise in this context. The interest in algal production in India is evidenced by the initiation of the All India Co-ordinated Project on Algae by the Department of Science and Technology. Several institutions in India are involved in this effort for utilising algae as a biofertiliser, fuel and feed (AICPA, 1976-80). In this endeavour the use of rural wastes in algal biomass production, as discussed here, will form a significant part. It is hoped that the ideas for utilising rural waste, as suggested in this study, will provoke more work on algal productivity.

Air exhaust

~,%x~xxx x~

Glass

plate

Door

Door

:6ox6Io •

Fermentable

material

in tr oys

~,.~[-~lAir

2"8M

,~, ~5 % Fig. 8.

25

~k

200

~y

J

B

%

25

% 15%

Rural type fermenter for CO 2 enriched air (aerobic biogas) production. (Scale in centimetres.)

RURAL WASTES FOR ALGAL PRODUCTION

129

ACKNOWLEI)GEMENTS T h i s p a p e r f o r m s a p a r t o f the w o r k o f the A l g a l P r o j e c t at the C e n t r a l F o o d T e c h n o l o g i c a l R e s e a r c h I n s t i t u t e , M y s o r e , India. T h e w o r k is p a r t o f a coll a b o r a t i o n b e t w e e n the G o v e r n m e n t s o f I n d i a a n d the F e d e r a l R e p u b l i c o f G e r m a n y a n d is also c o n d u c t e d u n d e r the All I n d i a C o - o r d i n a t e d P r o j e c t on A l g a e , f i n a n c e d by the D e p a r t m e n t o f S c i e n c e a n d T e c h n o l o g y ( D S T ) , India. T h e a u t h o r s t h a n k their c o l l e a g u e s for a s s i s t a n c e d u r i n g the c o u r s e o f this w o r k . T h e y also t h a n k the D i r e c t o r , C. P. N a t a r a j a n ; the D e p u t y D i r e c t o r , P. K. R a m a n a t h a n , C F T R I , M y s o r e , for s h o w i n g i n t e r e s t in the w o r k , a n d M r K. M. D a s t u r , C F T R 1 , for e d i t i n g the p a p e r .

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