Enhanced vermicomposting of rice straw and pressmud with biogas slurry employing Eisenia fetida: Production, characterization, growth, and toxicological risk assessment

The biogas plant plays a dual role: it directly provides energy and indirectly promotes organic farming through outlet slurry. However, agricultural biomass wastes such as rice straws (RS) and pressmud (PM), which can't be used as fertilizers on their own, were vermicomposted (60 days) with biogas slurry (BS), using earthworm, into four blends: T1(BS, 100%), T2(3:2, BS: RS), T3(3:2, BS: PM), and T4(3:1:1, BS: RS: PM). The characterization, elemental analysis, and toxicological risk assessment of derived vermimanure were carried out using various analytical tools, such as an organic elemental analyzer such as CHNS, FT-IR, FESEM-EDXA, XPS, and ICP-OES. The pH, electrical conductivity, and C/N values were within 7.1-7.8, 3.2-6.0 dSm-1, and 12-15, respectively, for all treatments. The proportions of N (38%), P (70%), K (58%), Mg (67%), Ca (42%), and ash (44%), increased significantly (P < 0.05) over the initial feedstocks. The ecological risks of heavy metals (Zn, Cu, Ni, Pb, Cd, and Cr) in all feedstocks were found to be under WHO-permitted levels. The growth performance of earthworms was also considerably higher (P < 0.05) over the control feedstock group. The analytical methods verified that feedstock T4 (3:1:1, BS: RS: PM) was more porous, containing NH4+, PO43-, K+, and other nutrients. Pellets of all vermimanure groups keep 65-75% of the original volume. As well, when these pellets have been employed for agronomy and dispersed in the field, they will cause less dust than traditional or powdered compost or manure. In comparison to the control group, the synergistic approach of RS, PM, and BS in vermimanure significantly (P < 0.05) enhanced seed germination (83%), vigour index (42.5%), and decreased mean germination time by 27%. Furthermore, pot trials with Abelmoschus esculentus seed indicated that seedlings cultivated with 40% vermimanure of T4 (3:1:1, BS: RS: PM) mixed soil showed high growth in shoot, root, and plant yield.

Extraction and identification of endopeptidases in convection dried papaya and pineapple residues: A methodological approach for application to higher scale

The use of agro-industrial waste for application in the obtention of products with high added value has become a trend in recent years, especially in tropical countries whose main economic sector is agricultural exports. In the present study, an applicable method to food industry of extracting proteolytic enzymes from dryed papaya and pineapple residues by convection was developed. Different to other scientific reports the heat treatment at 40 °C of waste residues, to reach 20% moisture, allowed an increase in total soluble protein content and did not alter the proteolytic activity of the extracts when phosphate buffer pH 7.0 was used as solvent. In the residues evaluated as candidates for the extraction of endopeptidases, we observed that green dried papaya peel and dried pineapple core, had higher activity values (914.34 ± 25.47 U/mg and 2152.36 ± 75.99 U/mg, respectively). These results, combined with one-dimensional electrophoresis and protein identification methods by MALDI TOF-TOF, showed the presence of signal peptides characteristic of papain, bromelain and other endopeptidases previously reported in extracts of fresh papaya and pineapple residues. These findings show that the drying of the residues by convection does not alter neither the activity nor the structure of the proteolytic enzymes. Finally, it is confirmed that the use of 20% ammonium sulfate as a precipitating agent allows to reach an efficiency of 74% in different work scales the use of purification and identification protocols in a more adaptable way, making them the most promising waste in Colombia, due to its potential for the production of bromelain on a larger scale.

Development and evaluation of a new multi-metal binding biosorbent

A novel multi-metal binding biosorbent (MMBB) was developed by combining a group of three from the selective natural lignocellulosic agro-industrial wastes for effectively eliminating lead, cadmium, copper and zinc from aqueous solutions. Four MMBBs with different combinations (MMBB1: tea waste, corncob, sugarcane bagasse; MMBB2: tea waste, corncob and sawdust; MMBB3: tea waste, corncob and apple peel; MMBB4: tea waste, corncob and grape stalk) were evaluated. FTIR analysis for characterizing the MMBB2 explored that the MMBB2 contains more functional groups available for multi-metals binding. Comparing among the MMBBs as well as the single group biosorbents, MMBB2 was the best biosorbent with the maximum biosorption capacities of 41.48, 39.48, 94.00 and 27.23 mg/g for Cd(II), Cu(II), Pb(II) and Zn(II), respectively. After 5 times of desorption with CaCl2, CH3COOH and NaCl as eluent, the MMBB2 still remained excellent biosorptive capacity, so as it could be well regenerated for reuse and possible recovery of metals.