Thermostable Acid Protease Produced by Penicillium duponti K1014, a True Thermophilic Fungus Newly Isolated from Compost

Abstract

A thermophilic fungus, K1014, newly derived from a compost was selected on the basis of protease productivity as the only one of 81 isolates to produce high levels of acid protease. The fungus was named Penicillium duponti K1014 based on taxonomical studies. It grew in the temperature range of 28 to 58 C, and the optimum was 45 to 50 C. These temperature characteristics showed that the fungus was the most strongly thermophilic of all the fungi next to Humicola lanuginosa . When P. duponti K1014 was grown on moistened wheat bran, maximal accumulation of acid protease occurred after 2 days at 45 to 50 C. The addition of ammonium salts, but not nitrate, was effective for the production of the acid protease. The acid protease of P. duponti K1014 was stable at 60 C for 1 hr and retained more than 65% of original activity after the treatment for 1 hr at 70 C at p H 4.7. This thermal property was different from those of the ordinary acid proteases, indicating that the enzyme is a thermostable protein.

Microbiota Dynamics of Mechanically Separated Organic Fraction of Municipal Solid Waste during Composting

“…The genera Penicillium , Aspergillus , and Agaricus can also be attributed to the fungal dominants of the initial substrate. Though Penicillium is considered mesophilic, it has been detected during high-temperature composting by other researchers [ 42 , 43 , 44 ]. These microorganisms used easily degradable OM, whose content was initially high in ms-OFMSW.…”

Development of a microbial protease for composting swine carcasses, optimization of its production and elucidation of its catalytic hydrolysis mechanism

“…Microorganisms in compost are responsible for degradation of organic matter, although an insufficient number of indigenous microorganisms or limited enzyme production capacity may impair biodegradability [ 9 ]. However, biodegradability of compost can be improved by inoculation with enzyme preparations [ 10 , 11 ] or enzyme-producing microorganisms; the latter can secrete extracellular enzymes to hydrolyze organic matter, thereby increasing compost biodegradability [ 12 , 13 ]. In addition, inoculation of enzyme preparations into compost significantly hastened degradation of organic matter [ 14 ], with more direct action than adding microorganisms to produce enzymes.…”