Studies on biomass production in Auricularia polytricha collected from Wilberforce Island, Bayelsa State, Nigeria

American Journal of Applied Sciences, Jan, 2009 by S.G Jonathan, D.D.S Bawo, D.O. Adejoye, O.F. Briyai

INTRODUCTION

Previous work have been carried out on collection, identification and isolation of indigenous Nigerian mushrooms (1), (2), (3), (4), (5) .Investigations were carried out on these fungi basically, to determine their nutritional requirements and utilization in biotechnological processes. These organisms have been implicated in lignin and other recalcitrant substances degradation, soil bioremediation, production of edible biomass and secondary metabolites (6), (7), (8), (9) Auricularia polytricha is widely distributed throughout the tropical and subtropical regions of the world (10), (27). It belongs to phyllum basidiomycota, order auriculariales and family auriculariaceae (11). This edible mushroom species is the commonest among the jelly-like fungi in West Africa. It grows wildly during the rainy season within the bark of a decaying wood under shade (3), (10), (11). The sporophores of this fungus are usually found in their large numbers during late July.

Auricularia polytricha has a very peculiar consistency. The basidiocarp when fresh is rubbery, gelatinous and ear-like in structure but when dried, it is shapeless and brittle. Its edible fruitbodies could be easily identified by pilose upper surface which is strongly capitate with dark brown smooth hymenium (3), (10). Fungal biomass have been found to be important for several purposes (i) It could be of immense advantage for process reduction in fermentation technology (12) (ii) Fungal biomass could be used as food or protein supplement (13)(iii) Fungal biomass could be used for flavour extraction (14)(iv) They could be used for extraction of metabolites such as polysaccharides and enzymes(15)(v) They could also be used for wound treatment (16).

The primary objective of the present studies is therefore to culture A. polytricha in sub-merged liquid medium under different physico-chemical parameters with the aim of producing high yield biomass of this fungus.

MATERIALS AND METHODS

Micro-organism: Auricularia polytricha (Mont) Saccardo were found growing on logs of decaying wood in their large numbers within the marshy riverine ecosystem in Amassoma, Wilberforce Island, Bayelsa State, Nigeria. The sporophores of this fungus were tissue cultured and the mycelia culture thus obtained were maintained on Malt extract agar (Difco) (2), (17)

Effect of incubation temperature on biomass production: The effect of incubation temperature on biomass production in A. polytricha was determined in a chemically defined medium. This medium has the following compositions (g [L.sup.-1]) glucose 10.0 yeast extract 3.0, [K.sub.2] HP[O.sub.4].0.6 [H.sub.o] following compositions (g [L.sup.-1]) glucose 10.0 yeast extrac6 3.0, [K.sub.2] HPO.sub.4].7 [H.sub.o.3, IL of distilled water ad pH of 6.20 (170. The basal medium was dispensed into 250c[m.sup.3] conical flasks (100 c[m.sup.3] per flask). Each was coverd with aluminum foil and sterilized i the autoclave at 1.02 ke cm(-2) at 121[degree]C for 15 min. After cooling, each flask was inoculated with vigorously growing (5 day old fungus) acid incubated at 5,10,15,20,25,30,35,40,45 and 50 [degree] C respectively for 5,10,15 and 20 days. Each treatment was replicated three time. The mycelial biomass produced were harvested using the method of Gbolagade et al (4).

Effect of pH on biomass production in A. polytricha: For pH, the same basal medium used for temperature determination was employed. The medium pH was adjusted to 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5 and 9.5. 100 cm3 of each treatment was dispensed into 250 cm3 conical flasks and replicated thrice. They were autoclaved at 121[degrees]C and 1.02 kg cm-2 for 15 min. After cooling, they were inoculated and biomass produced were harvested as described in the temperature experiment.

Utilization of different concentration of carbon compounds for biomass production in A. polytricha: Four carbon sources namely glucose, fructose, mannitol and cellulose were evaluated. The concentration of these carbohydrate compounds used varies between 0.2-2.0% while the basal medium that lack any carbon compound (0%) served as the control. The fermentation medium has the following For compositions in percentage (%): peptone 0.2, MgSO4. 7H2O 0.1, K2H PO4. 3H2O 0.1 and 1000 cm3 of distilled water (18). Each concentration of these carbon compounds was supplemented in the basal medium and the experiment were replicated three times.

Utilization of different concentration of nitrogen compounds for biomass production in A. polytricha: Four different sources of organic and inorganic nitrogen sources were used. These were alanine, tryptophan, ammonium sulphate and peptone. Fermentation medium was similar to the one of carbon sources but the nitrogen sources were replaced at an equivalent concentration. Various concentration of nitrogen compounds supplemented in this medium ranges from 0.01-0.12 (Table 4).

Table 4: Utilization of different concentrations of
nitrogen compounds for biomass production in A. polytricha

                  Biomass production (mg/100 [cm.sup.3])

[N.sub.2]
Compounds
Concentration    Alanine     Tryptophan  ([NH.sub.4]).sub.2  Peptone
in %                                        [So.sub.4]

0                  20h          20k             20h              20k
0.01               70f          40j             50ef             30jk
0.02               100e         60ij            50ef             40ij
0.03               150d         75hi            120ab            70h
0.04               190bc        95g             110b             100g
0.05               230a         120f            90cd             160f
0.06               180c         170e            75d              210d
0.07               155d         240d            70d              275c
0.08               115e         290bc           45f              320a
0.09               70f          285 ab          40fg             290bc
0.10               50g          300a            30gh             210d
0.12               50g          250de           30gh             185ef

Values followed by the same letter(s) along each column
are not significantly different by Duncan's multiple
range. Data are means of 3 replicates