Identification of intralocus recombinants for the mating loci of Lentinula edodes.

Mating type analysis was carried out for progeny of 13 strains of Lentinula edodes. Out of the 13 strains, one strain HL01 was found with an exceptional phenotype, in that the proportion of incompatibility to compatibility of 132 random pairings of monokaryons derived from the dikaryon was 82:50. This value differs significantly (Chi-square = 11) from the expected 3:1 ratio. The mating types of 189 monokaryons derived from the same sporocarp of HL01 were identified using four standard tester strains. Of the 189 spore monokaryons, 161 monokaryons could be classified into one of four normal mating types (A(1)B(1), A(2)B(2), A(1)B(2), and A(2)B(1)), and the other 28 monokaryons could be classified into another four groups. By crossing in all pairwise combinations, the mating types of the 28 monokaryons were further analyzed. The results indicated that intralocus recombination occurred in both A and B mating loci (matA and matB), at frequencies of 8.5 and 11.6%, respectively. The matA is composed of at least two subloci while the matB may be composed of more than two subloci. The subsequent fruiting test revealed that all compatible pairings which contained at least one of the recombinants had the ability to produce fruiting bodies.

Numerical model of aerobic bioreactor landfill considering aerobic-anaerobic condition and bio-stable zone development.

Aeration by airflow technology is a reliable method to accelerate waste biodegradation and stabilization and hence shorten the aftercare period of a landfill. To simulate hydro-biochemical behaviors in this type of landfills, this study develops a model coupling multi-phase flow, multi-component transport and aerobic-anaerobic biodegradation using a computational fluid dynamics (CFD) method. The uniqueness of the model is that it can well describe the evolution of aerobic zone, anaerobic zone, and temperature during aeration and evaluate aeration efficiency considering aerobic and anaerobic biodegradation processes. After being verified using existing in situ and laboratory test results, the model is then employed to reveal the bio-stable zone development, aerobic biochemical reactions around vertical well (VW), and anaerobic reactions away from VW. With an increase in the initial organic matter content (0.1 to 0.4), the bio-stable zone expands at a decreasing speed but with all the horizontal ranges larger than 17 m after an intermittent aeration for 1000 days. When waste intrinsic permeability is equal or greater than 10-11 m2, aeration using a low pressure between 4 and 8 kPa is appropriate. The aeration efficiency would be underestimated if anaerobic biodegradation is neglected because products of anaerobic biodegradation would be oxidized more easily. A horizontal spacing of 17 m is suggested for aeration VWs with a vertical spacing of 10 m for screens. Since a lower aeration frequency can give greater aeration efficiency, a 20-day aeration/20-day leachate recirculation scenario is recommended considering the maximum temperature over a reasonable range. For wet landfills with low temperature, the proportion of aeration can be increased to 0.67 (20-day aeration/10-day leachate recirculation) or an even higher value.

CFD modeling of hydro-biochemical behavior of MSW subjected to leachate recirculation.

The most commonly used method of operating landfills more sustainably is to promote rapid biodegradation and stabilization of municipal solid waste (MSW) by leachate recirculation. The present study is an application of computational fluid dynamics (CFD) to the 3D modeling of leachate recirculation in bioreactor landfills using vertical wells. The objective is to model and investigate the hydrodynamic and biochemical behavior of MSW subject to leachate recirculation. The results indicate that the maximum recirculated leachate volume can be reached when vertical wells are set at the upper middle part of a landfill (H W/H T = 0.4), and increasing the screen length can be more helpful in enlarging the influence radius than increasing the well length (an increase in H S/H W from 0.4 to 0.6 results in an increase in influence radius from 6.5 to 7.7 m). The time to reach steady state of leachate recirculation decreases with the increase in pressure head; however, the time for leachate to drain away increases with the increase in pressure head. It also showed that methanogenic biomass inoculum of 1.0 kg/m3 can accelerate the volatile fatty acid depletion and increase the peak depletion rate to 2.7 × 10-6 kg/m3/s. The degradation-induced void change parameter exerts an influence on the processes of MSW biodegradation because a smaller parameter value results in a greater increase in void space.