1 Plant Archives Vol. 20, Supplement 2, 2020 pp. 3458-3463 e-ISSN:2581-6063 (online), ISSN:0972-5210 BIOPROSPECTING ANTIMICROBIAL POTENTIAL OF LIGNIN STREAM OF PADDY STRAW AGAINST FOOD-BORNE PATHOGENS Punmeet Kaur 1 , Sweety Kaur 2 , Richa Arora 3* School of Bioengineering and Biosciences, Lovely Professional University, Phagwara, Punjab, India Present address: Nestle India Limited, Rajarhat, Kolkata, India 1 E-mail: punmeetsondh@gmail.com, 2 E-mail: sweetykaurasr@gmail.com, 3 E-mail: aroraricha@ymail.com Abstract The present study was carried out to exploit the antimicrobial potential of lignin extracts obtained from four varieties of paddy straw i.e. PUSA-44, PR-111, PR-114, PR-122 against Aeromonas hydrophila (MTCC 1739), Klebsiella pneumoniae (MTCC 7028), Escherichia coli (MTCC 739) and Staphylococcus aureus (MTCC 96). Antimicrobial activity was tested both qualitatively w.r.t. zone of inhibition (ZOI) and quantitatively w.r.t. minimum inhibitory concentration (MIC). The best results were shown by lignin obtained from PR-122, where ZOI (mm) and MIC (μg/ml) for A. hydrophila, K. pneumoniae, E. coli and S. aureus were found to be 25 and 50, 19.3 and 50, 20 and 100, 18.6 and 100, respectively. Further, the lignin extracts were characterized using FT-IR spectrum and zeta potential. The present study exploits the immense potential of valorization of lignin-stream obtained from paddy straw in food and pharma industries. Keywords: lignin valorization; stubble paddy straw burning; food-borne pathogens; minimum inhibitory concentratio. Introduction The current challenges of energy crisis and greenhouse gas emissions (Kotia et al., 2019; Kotia et al., 2017a) has led to the exploitation of second generation raw materials for bioenergy production and other applications in biorefinery manner (Arora et al., 2015; Chahartaghi et al., 2019; Jilte et al., 2019; Kumar et al., 2018; Bhardwaj et al., 2014; Duran et al., 2015; Sharma et al., 2019; Kotia et al., 2016a; Churasia et al., 2016; Ghazvini et al., 2020; Kumar et al., 2003; Kumar and Kumar, 2018; Kotia et al., 2018). However, out of the three major components (cellulose, hemicellulose and lignin) of lignocellulosic raw materials, valorization of lignin needs much attention. The materialization of the biorefinery is currently focused as the area of interest that transforms lignocellulosic biomass to products of potential uses (Sharma et al., 2018; Vyas et al., 2018; Kotia et al., 2018; Kotia et al., 2016b; Chauhan et al., 2015; Patel et al., 2017; Jha et al., 2019; Priyadarshi et al., 2019; Jha et al., 2019; Kotia and Ghosh, 2015; Kotia et al., 2016c). Lignin is an amorphous polymer crosslinked by phenolic units which furnishes structural integrity in the plants (Brethauer and Studer, 2015; Calvo-Flores and Dobado, 2010; Singh et al., 2013; Gupta et al., 2012; Kalra and Kumar, 2018; Yadav et al., 2011; Vyas et al., 2010). Due to the inherent property of lignin as inexhaustible and inexpensive to produce various biomaterials, lignin’s substitution prospective expands to replace products derived from contrasting mediums (Watkins et al., 2015; Pramanil and Maji, 2015; Pramanik and Padan 2016). The flexibility in lignin monomer composition has been proven to be useful for enhancing the production of biomaterials (Ragauskas et al., 2014). On the other hand, many foodborne pathogens have become resistant to the synthetic drugs (Arora et al., 2012; Korekar et al., 2011). Hence, plant-based drugs and antimicrobial products are extensively used as traditional antibiotics attributable to their effectiveness and prevention of emergence of new diseases (Beisl et al., 2017). Three basic phenolic derivatives including sinapyl alcohol (S) p- coumaryl alcohol (H) and coniferyl alcohol (G) have been reported in the literature with high antimicrobial activity. Antimicrobial activities of phenol ring is due to its property to delocalize and stabilize the unpaired electrons (Cheetangdee, 2019; Anup et al., 2000; Arora et al., 2015; Chowdary et al., 2019; Chilana et al., 2015; Sharma et al., 2014; Manna et al., 2017). The hydroxyl group present in the phenolic moiety of lignin interacts with cell membrane of microbes (Kumar et al., 2013; Gupta et al., 2013), thereby destructing the lipid bilayer and increases the permeability of cell membrane causing leakage of the cell components (Sriroth and Sunthornvarabhas, 2018; Spasojevic et al., 2016; Papuc et al., 2017). The usage of phenolic compounds aids in food preservation and food processing because of the raised awareness among the consumers of natural based food products and the increasing antibiotic resistance (Dong et al., 2011; Cein-Karaka and Newman, 2015; Kumar et al., 2020; Kaur et al., 2014; Kaur et al., 2019; Sangma et al., 2019). Moreover, the exploration of phenolic compounds can provide extra benefits on the food packaging as well as on the health care services (Espinoza-Acosta et al., 2016). Presence of coumaric acid in lignin has also observed to exhibit free radical scavenging activity (Kaur and Uppal, 2015; Upton and Kasko, 2015; Fernandes et al., 2013) which is helpful in curing cancer (Ugartonda et al., 2008; Kumar and Mistri, 2019) and cardiovascular diseases (Boz, 2015). Thus, biodegradability, abundance, neutrality to harmful gases, cost efficient, eco-friendly and biocidal properties of lignin exhibit promising applications (Thakur et al., 2014). The present study was carried out with the objective to valorize the lignin stream obtained from paddy straw and to exploit its antimicrobial potential, both qualitatively and quantitively, against food-borne pathogens viz. Aeromonas hydrophila (MTCC 1739), Klebsiella pneumoniae (MTCC