Screening and selection of the strains
Table 1 shows the colony characteristics of the different strains of Lentinus sp. screened.
Although all the strains grew on coffee husk extract medium, strain L. edodes LPB 02
showed best growth, with 7.57 mm/day mycelial growth and 48.78 mg/plate biomass in
12 days at 24C. Hence, this strain was used in further investigation.
SSC using raw coffee husk
Fig. 1a shows the change of contents of the protein and fibre in raw coffee husk during
25 days SSC. The reason for selecting the period of 25 days for SSC was that that after this
period, the mycelia of Lentinus sp. tended to enter to the maturity phase and transformed
brownish in colour (FAN and DING 1990). Evidently, the protein content in the substrate
increased with the time course of SSC and the fibre content decreased. Although, the increase
in the protein content and decrease in the fibre content were not substantially high,
considering the toxic nature of the substrates, these were considered significant. There are (CHANG 1989, FAN and DING 1990, ZADRAZIL 1985). However, with coffee husk, to the
best of our knowledge, this is the first report.
Fig. 1b shows the effect of different moisture level in coffee husk after 25 days of
growth. As is apparent, the substrate with 55–60% moisture resulted maximum protein and
minimum fibres. The mycelial growth in this case was very vigorous (visual observation).
At 45% substrate moisture, the growth as evidenced by visual observation and protein content
was lowest. When the substrate moisture was 75%, the fermentation was very poor and
was almost comparable to that with 45%. Optimum level of moisture has been termed as a
crucial factor in SSC (PANDEY 1992a, b). High moisture level results in decreased substrate
porosity, preventing oxygen transfer. Low moisture level leads to poor accessibility of
nutrients to the microbial culture, resulting poor growth. CHANG (1989), FAN and DING
(1990) and YANG (1986), who reported that 60% moisture was most suitable for mushroom
production in SSC have also discussed importance of moisture in SSC for cultivating edible
fungus.
Fig. 1c shows the effect of different spawn rate on the protein and the fibre contents of
coffee husk after 25 days of SSC. With increase in spawn rate, there was an increase in the
content of the protein and decrease in the fibres content, showing 25% spawn rate as the
best. However, there was not much difference in the protein contents between 10–25%
spawn rate. Considering the economics of the process using 10 and 25% spawn rates, we considered a spawn rate of 10% as suitable. Moreover, we did not face any contamination
problem with 10% spawn rate. Spawn rate has been considered as one of the principal factors
for edible fungus cultivation in SSC. There are reports described different spawn rates
using different substrates for mushroom cultivation. RAJARATHNAM and BANO (1987) reported
that the spawn rate less than 10% facilitated contamination and decreased the biological
efficiency. They recommended higher (20%, or more) spawn rate. Our findings
were confined to laboratory conditions. For use in large-scale process, the substrate with
low spawn rate could be prone to mould infection and higher inoculum rate might be required.
This could be more important when mushroom production is concerned for human
food, as it must be protected from mould spoilage.
Screening and selection of the strainsTable 1 shows the colony characteristics of the different strains of Lentinus sp. screened.Although all the strains grew on coffee husk extract medium, strain L. edodes LPB 02showed best growth, with 7.57 mm/day mycelial growth and 48.78 mg/plate biomass in12 days at 24C. Hence, this strain was used in further investigation.SSC using raw coffee huskFig. 1a shows the change of contents of the protein and fibre in raw coffee husk during25 days SSC. The reason for selecting the period of 25 days for SSC was that that after thisperiod, the mycelia of Lentinus sp. tended to enter to the maturity phase and transformedbrownish in colour (FAN and DING 1990). Evidently, the protein content in the substrateincreased with the time course of SSC and the fibre content decreased. Although, the increasein the protein content and decrease in the fibre content were not substantially high,considering the toxic nature of the substrates, these were considered significant. There are (CHANG 1989, FAN and DING 1990, ZADRAZIL 1985). However, with coffee husk, to thebest of our knowledge, this is the first report.Fig. 1b shows the effect of different moisture level in coffee husk after 25 days ofgrowth. As is apparent, the substrate with 55–60% moisture resulted maximum protein andminimum fibres. The mycelial growth in this case was very vigorous (visual observation).At 45% substrate moisture, the growth as evidenced by visual observation and protein contentwas lowest. When the substrate moisture was 75%, the fermentation was very poor andwas almost comparable to that with 45%. Optimum level of moisture has been termed as acrucial factor in SSC (PANDEY 1992a, b). High moisture level results in decreased substrateporosity, preventing oxygen transfer. Low moisture level leads to poor accessibility ofnutrients to the microbial culture, resulting poor growth. CHANG (1989), FAN and DING(1990) and YANG (1986), who reported that 60% moisture was most suitable for mushroomproduction in SSC have also discussed importance of moisture in SSC for cultivating ediblefungus.Fig. 1c shows the effect of different spawn rate on the protein and the fibre contents ofcoffee husk after 25 days of SSC. With increase in spawn rate, there was an increase in thecontent of the protein and decrease in the fibres content, showing 25% spawn rate as thebest. However, there was not much difference in the protein contents between 10–25%spawn rate. Considering the economics of the process using 10 and 25% spawn rates, we considered a spawn rate of 10% as suitable. Moreover, we did not face any contaminationproblem with 10% spawn rate. Spawn rate has been considered as one of the principal factorsfor edible fungus cultivation in SSC. There are reports described different spawn ratesusing different substrates for mushroom cultivation. RAJARATHNAM and BANO (1987) reportedthat the spawn rate less than 10% facilitated contamination and decreased the biologicalefficiency. They recommended higher (20%, or more) spawn rate. Our findingswere confined to laboratory conditions. For use in large-scale process, the substrate withlow spawn rate could be prone to mould infection and higher inoculum rate might be required.This could be more important when mushroom production is concerned for humanfood, as it must be protected from mould spoilage.
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