Agriculture Reference
In-Depth Information
Eida et al. ( 2012 ) reported the isolation and characterization of cellulose decompos-
ing bacteria from saw dust and coffee residue composts. A number of thermophilic
bacteria belonging to the genus Paenibacillus , Cohnella , Streptomyces and Micro-
biospora were identified using 16S rRNA gene analysis. The two strains belonging
to P. woosongensis were found to produce many hydrolytic enzymes, including cel-
lulases, xylanases, β-glucanase, and mannanase. Kim et al. ( 2012 ) reported the iso-
lation of hundreds of cellulolytic bacteria based on the screening of different com-
post samples from Jeju Island, South Korea. Based on qualitative screening three
potential strains with high cellulolytic activity were identified as Bacillus subtilis
based on 16S rRNA gene sequencing. CMCase and Avicelase activities were de-
tected in the extracellular fraction, while β-glucosidase activity was found to be cell
bound. Shu-bin et al. ( 2012 ) reported the isolation and identification of B. subtilis
strain Pa5 from soil samples rich in rotting rice straw. The optimal pH and tempera-
ture for both CMCase and cellobiase were observed at pH 7.0 and 50 °C. The en-
zyme exhibited a broad range of thermostability (30 to 50 °C) and pH stability (5.0-
8.0). Nizamudeen and Bajaj ( 2009 ) reported the isolation of numerous cellulolytic
bacteria from different lignocellulosic sources. They identified a highly thermotol-
erant and alkali-tolerant endoglucanase producing Bacillus sp. NZ. Maximum en-
zyme production was observed after 72 h at 45 °C and pH 9.0. High endo-glucanase
activity was observed with wheat straw, filter paper and saw dust as lignocellulosic
substrates. The enzyme was active over a broad pH (5-10) and temperature (50-
100 °C) range. The enzyme exhibited maximum activity at pH 9-10 and at two dif-
ferent temperatures 50 and 90 °C. The enzyme was highly stable for 30 min from 60
to 90 °C. Thermophilic bacterial strains and their hydrolytic enzymes produces dur-
ing different stages of composting process is tabulated in Table 6.1 .
6.8
Future Prospects and Recommendations:
The Ecological and Economic Impact of Composting
with Special Reference to Agricultural Residues
Agricultural crop residues including field residues and processing residues are re-
newable and abundant resources that contain large amounts of untapped energy. The
crop residues (including lignocellulosic biomass) in the form of hot composts offer
an intricate ecosystem that provides the natural selection for the isolation of ther-
mophilic cellulolytic and lignocellulolytic bacteria. The isolation of Bacillus and
Geobacillus sp. reported above provides ample support towards the application of
composting for the generation of biofuels. The use of engineered strains as special
additions during the thermophilic phase of the composting process can be used as
an effective strategy for consolidated bioprocessing. Rice straw, wheat straw, corn
stover and sugarcane bagasse are the major agricultural wastes in terms of quantity
of biomass available and it is estimated by Kim and Dale ( 2004 ) that the potential
production of 49.1 GL year −1 of bioethanol from 73.9 × 10 6 t of dry waste crops
available in the world. The lignocellulosic biomass from the seven major crops ac-
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