RESUMEN
The study identified the innate enzymatic potential (amylase) of the PHB producing strain B.thuringiensis IAM 12077 and explored the same for cost-effective production of PHB using agrowastes, eliminating the need for pretreatment (acid hydrolysis and/or commercial enzyme). Comparative polyhydroxyalkanoate (PHA) production by B. thuringiensis IAM 12077 in biphasic growth conditions using glucose and starch showed appreciable levels of growth (5.7 and 6.8 g/L) and PHA production (58.5 and 41.5%) with a PHA yield of 3.3 and 2.8 g/L, respectively. Nitrogen deficiency supported maximum PHA yield (2.46 g/L) and accumulation (53.3%). Maximum growth (3.6 g/L), PHB yield (2.6 g/L) and PHA accumulation (72.8%) was obtained with C:N ratio of 8:1 using starch as the carbon source (10 g/L). Nine substrates (agro and food wastes) viz. rice husk, wheat bran, ragi husk, jowar husk, jackfruit seed powder, mango peel, potato peel, bagasse and straw were subjected to two treatments- acid hydrolysis and hydrolysis by innate enzymes, and the reducing sugars released thereby were utilized for polymer production. All the substrates tested supported comparable PHB production with acid hydrolysis (0.96 g/L-8.03 g/L) and enzyme hydrolysis (0.96 g/L -5.16 g/L). Mango peel yielded the highest PHB (4.03 g/L; 51.3%), followed by jackfruit seed powder (3.93 g/L; 29.32%). Varied levels of amylase activity (0.25U-10U) in all the substrates suggested the enzymatic hydrolysis of agrowastes.
RESUMEN
Mango peel, a solid mango processing waste, comprises 15-20% of total fruit weight. This, being a rich source of lignocelluloses, was used as substrate for carboxymethyl cellulase (CMCase) production using Paenibacillus polymyxa. Maximum CMCase production (7.814 U mg-1) was observed in a medium containing 7% mango peel (w/v) with 1.5% ammonium sulphate (w/v) at 37oC and pH 5.5. Purification to an extent of 28.24 fold was achieved by affinity column chromatography. Bands corresponding to 26.5 and 34.0 kDa molecular sizes were observed on 12% denaturing Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) while of 72 kDa on 10% non- denaturing Native-PAGE, proving its heteromeric multienzyme nature. The enzyme was stable over a range of 20-60oC and pH of 4.0-7.5. Michaelis-Menten equation constant (Km and Vmax) values of purified CMCase were 8.73 mg ml-1 and 17.805 mM ml-1 min-1, respectively.
RESUMEN
In an ongoing project to evaluate natural compounds isolated from by-products or wastes from vegetables and fruits (edible plants) as modulators of antibiotic resistance, ethanol extract from mango peel was investigated using Staphylococcus aureus strains possessing efflux mechanisms of resistance to norfloxacin, erythromycin and tetracycline. The minimum inhibitory concentrations (MIC) of the antibiotics were determined by the micro dilution assay in the absence and in the presence of sub-inhibitory mango peel extract concentration. Although the extract did not display relevant antibacterial activity (MIC>2048 µg/mL), it modulated the activity of antibiotics, i.e. in combination with antibiotics (at 512 µg/mL), a four-fold reduction in the MIC values for tetracycline and erythromycin was observed. The results presented here indicates that mango peel could serve as a source of potential adjuvant of antibiotics which add value to this mango by-product.