Genotoxic assessment and optimization of pressmud with the help of exotic earthworm Eisenia fetida

Abstract

Genotoxicity of pressmud (PM) to Allium cepa was investigated to assess its toxic potential and to elucidate the effect of vermicomposting to reduce its toxicity. The PM produced as a waste by product of the sugar cane industry was mixed with cow dung (CD) at different ratios of 0:100 (V₀), 25:75 (V₂₅), 50:50 (V₅₀), 75:25 (V₇₅) and 100:0 (V100) (PM:CD) on a dry weight basis for vermicomposting with Eisenia fetida. Different concentrations of 100% PM sludge extract (10%, 20%, 40%, 60%, 80% and 100%) and negative control (distilled water) and positive control (maleic hydrazide) were analyzed with A. cepa assay to evaluate frequency of chromosomal aberrations before and after vermicomposting. Percent aberration was greatest (30.8%) after exposure to 100% PM extract after 6 h but was reduced to 20.3% after vermicomposting. Exposure to the extract induced c-mitosis, delayed anaphase, laggards, stickiness and vagrant aberrations. Microscopic examination of root meristem exposed to PM sludge extract showed significant inhibition of mitotic index. Also, the mitotic index decreased with increase in concentration of PM sludge extract. After vermicomposting the mitotic index was increased. However, increasing percentages of PM significantly affected the growth and fecundity of the worms and maximum population size was reached in the 25:75 (PM:CD) feed mixture. Nitrogen, phosphorus, sodium, electrical conductivity (EC) and pH increased from initial feed mixture to the final products (i.e., vermicompost), while organic carbon, C/N ratio and potassium declined in all products of vermicomposting. Scanning electron microscopy (SEM) was recorded to identify the changes in texture with numerous surface irregularities and high porosity that proves to be good vermicompost manure. It could be concluded that vermicomposting could be an important tool to reduce the toxicity of PM as evidenced by the results of genotoxicity.

Management of Sugar Industrial Wastes through Vermitechnology

“…The study revealed that earthworm growth and nutrient content was more in small scale vermireactor as compared to pilot scale vermireactor and may be due to microclimatic variability in feed mixtures. Bhat et al [2] managed pressmud sludge through E. fetida and observed that the maximum growth and reproduction was observed in the 25:75 (pressmud: cow dung) feed mixture. Bhat et al [3] also managed baggase waste amended with cattle dung through earthworm E. fetida.…”

“…During the processing of sugar, different kind of wastes is generated like pressmud, bagasse, sugar cane trash, sugar beet mud, pulp, molasses etc. [2][3][4][5]. These wastes are potential pollutants unless recycled.…”

“…The study indicated that the flyash can be managed into a nutrient rich material if mixed 40-60% with pressmud. Bhat et al [2] reported the genotoxicity reduction and vermicomposting of pressmud sludge amended with cow dung using E. fetida. The results showed that the nutrients like pH, electrical conductivity, nitrogen, phosphorus and sodium increased from initial to final feed mixtures while organic carbon, C:N ratio and potassium declined in all the products of vermicomposting.…”

“…In vermicomposting process, a decline in C:N ratio to less than 20 indicates an advanced degree of organic matter stabilization [31] and reflects a satisfactory degree of maturity of organic wastes [32]. Decrease in C:N ratio in vermicomposting process may be due to the microbial respiration and the mineralization of the organic compounds, which are reducing the weight and volume in the mixtures, and increases the total nitrogen content [2,33].…”

Instrumental characterization of organic wastes for evaluation of vermicompost maturity

“…The maturity of vermicompost process involves changes in texture and structure which can be determined through scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, thermogravimetry (TG) and ultraviolet-visible (UV-vis) spectroscopy techniques (Ravindran et al 2013;. SEM analysis provides essential information on surface morphology and numerous surface irregularities in the vermicomposted mixtures that confirms the maturity and degradation of waste by earthworms (Bhat et al 2014(Bhat et al , 2015a. The final vermicomposted mixtures revealed a more fragmented texture than initial waste mixtures.…”