Growth tolerance of Zygomycetes Mucor indicus in orange peel hydrolysate without detoxification
Artikel i vetenskaplig tidskrift, 2012
The capability of two zygomycetes strains, Mucor indicus and an isolate from tempeh (Rhizopus sp.), to
grow on orange peel hydrolysate and their tolerance to its antimicrobial activity, was investigated. Both
fungi, in particular M. indicus, tolerated up to 2% d-limonene in semi-synthetic media during cultivation
in shake flasks, under aerobic as well as anaerobic conditions. The tolerance of M. indicus was also tested
in a bioreactor, giving rise to varying results in the presence of 2% limonene. Furthermore, both strains
were capable of consuming galacturonic acid, the main monomer of pectin, under aerobic conditions
when no other carbon source was present. The orange peel hydrolysate was based on 12% (dry w/v)
orange peels, containing d-limonene at a concentration of 0.6% (v/v), which no other microorganism
has been reported to be able to ferment. However, the hydrolysate was utilised by M. indicus under
aerobic conditions, resulting in production of 410 and 400 mg ethanol/g hexoses and 57 and 75 mg fungal
biomass/g sugars from cultivations in shake flasks and a bioreactor, respectively. Rhizopus sp., however,
was slow to germinate aerobically, and neither of the zygomycetes was able to consistently germinate
in orange peel hydrolysate, under anaerobic conditions. The zygomycetes strains used in the present
study demonstrated a relatively high resistance to the antimicrobial compounds present in orange peel
hydrolysate, and they were capable of producing ethanol and biomass in the presence of limonene,
particularly when cultivated with air supply.
Zygomycetes
Mucor indicus
Orange peel
Ethanol
D-Limonene