Effect of caffeine and tannins on cultivation and fructification of Pleurotus on coffee husks

Abstract

The objective of this work was to study the effect of caffeine and tannins on Pleurotus sp. cultivation and to evaluate the feasibility of using coffee husks as substrate for mushroom cultivation. Eight strains of P. ostreatus and two strains of P. sajor-caju were screened on a medium prepared from agar extract of coffee husk. Based on best mycelial growth and biomass production, the strain P. ostreatus LPB 09 was selected for detailed studies. With the increase of caffeine concentration, the mycelial growth and the biomass production decreased, and no growth was observed when concentration of caffeine was 2500 mg/L. Furthermore, Pleurotus did not degrade the caffeine, but absorbed it. Tannin under 100 mg/L in the medium stimulated the growth of mycelia, but above 500 mg/L it had a negative effect. When the concentration reached 1000 mg/L, the fungus still survived and showed a certain tolerance to it. No tannic acid was found in the mycelia, but its concentration decreased in the medium. This fact confirmed that Pleurotus had the capacity of degrading tannic acid. Fructification occurred after 20 days of inoculation and the biological efficiency reached about 97% after 60 days. Caffeine content in the husk after cultivation was reduced to 60.7% and tannins to 79.2%. The results indicated the feasibility of using coffee husk without any pretreatment for the cultivation of Pleurotus.

Pleurotus ostreatus, mushrooms production using quick and cheap methods and the challenges to the use of coffee husk as substrate

“…The use of this residue as substrate for mushroom cultivation seems to be an interesting strategy to add economic value to this residue and prevent environmental pollution. Many studies successfully reported production of mushrooms in sterilized coffee husk (Fan et al, , 2003Dias et al, 2003;da Silva et al, 2012). However, in South America, mushrooms are an expensive food, especially when compared with meat, making its commercialization difficult, thus justifying investigations of cheap methods to cultivate mushrooms in coffee husk.…”

“…One of these characteristics seems to be presence of tannins and caffeine in the coffee husk, compounds that can exert toxic effect on P. ostreatus and Lentinula edodes (Beaux and Soccol, 1996;Pandey et al, 2000;Fan et al, 2003) and can significantly affect the fungal growth. Immersion in water or boiling can remove those compounds from the substrate (Table 5), leading to levels low enough to enable adequate mycelial growth and consequently, to an increase in mushroom yield, as observed in this study (Table 1).…”

“…In fact, prior researches showed inhibition or decrease of fungal growth due to high moisture level in coffee husk (Fan et al, 2000b;Dias et al, 2003). To avoid or minimize this problem, previous studies reported adjusting the moisture of the substrate 4 to 5 h before the autoclaving (Fan et al, , 2003. Moreover, supplementation with agroindustrial residues with high moisture holding capacity (e.g.…”

“…The coffee husk is rich in nutrients (Rodriguez and Gordillo, 2011). However, it also contains compounds such as caffeine, tannins and polyphenols (Fan et al, 2000a(Fan et al, , 2003, which can be toxic and limit the uses of this residue . Therefore, most coffee husk is discarded or burned leading to environmental pollution.…”

“…Aiming to give a destination to this agro-industrial residue, studies have been made to use coffee husk as substrate for mushroom production (Fan et al, 2003;Dias et al, 2003;da Silva et al, 2012). Furthermore, *Corresponding author: E-mail: mkasuya@ufv.br.…”