Influence of l-amino acids on aggregation and biofilm formation in Azotobacter chroococcum and Trichoderma viride.

AIM: The effects of l-amino acids on growth and biofilm formation in Azotobacter chroococcum (Az) and Trichoderma viride (Tv) as single (Az, Tv) and staggered inoculated cultures (Az-Tv, Tv-Az) were investigated. METHODS AND RESULTS: A preliminary study using a set of 20 l-amino acids, identified 6 amino acids (l-Glu, l-Gln, l-His, l-Ser, l-Thr and l-Trp) which significantly enhanced growth and biofilm formation. Supplementation of these amino acids at different concentrations revealed that 40 mmol l-1 was most effective. l-Glu and l-Gln favoured planktonic growth in both single and in staggered inoculated cultures, while l-Trp and l-Thr, enhanced aggregation and biofilm formation. Addition of l-Glu or l-Gln increased carbohydrate content and planktonic population. Principal component analysis revealed the significant role of proteins in growth and biofilm formation, particularly with supplementation of l-Trp, l-Thr and l-Ser. Azotobacter was found to function better as biofilm under staggered inoculated culture with Trichoderma. CONCLUSIONS: The results illustrate that amino acids play crucial roles in microbial biofilm formation, by influencing growth, aggregation and carbohydrates synthesized. SIGNIFICANCE AND IMPACT OF THE STUDY: The differential and specific roles of amino acids on biofilm formation are of significance for agriculturally important micro-organisms that grow as biofilms, colonize and benefit the plants more effectively.

Chemical and microbiological changes during vermicomposting of coffee pulp using exotic (Eudrilus eugeniae) and native earthworm (Perionyx ceylanesis) species.

Coffee pulp is the main solid residue from the wet processing of coffee berries. Due to presence of anti-physiological and anti-nutritional factors, coffee pulp is not considered as adequate substrate for bioconversion process by coffee farmers. Recent stringent measures by Pollution Control authorities, made it mandatory to treat all the solid and liquid waste emanating from the coffee farms. A study was conducted to evaluate the efficiency of an exotic (Eudrilus eugeniae) and a native earthworm (Perionyx ceylanesis) from coffee farm for decomposition of coffee pulp into valuable vermicompost. Exotic earthworms were found to degrade the coffee pulp faster (112 days) as compared to the native worms (165 days) and the vermicomposting efficiency (77.9%) and vermicompost yield (389 kg) were found to significantly higher with native worms. The multiplication rate of earthworms (280%) and worm yield (3.78 kg) recorded significantly higher with the exotic earthworms. The percentage of nitrogen, phosphorous, potassium, calcium and magnesium in vermicompost was found to increase while C:N ratio, pH and total organic carbon declined as a function of the vermicomposting. The plant nutrients, nitrogen (80.6%), phosphorus (292%) and potassium (550%) content found to increase significantly in the vermicompost produced using native earthworms as compared to the initial values, while the calcium (85.7%) and magnesium (210%) content found to increase significantly in compost produced utilizing exotic worms. Vermicompost and vermicasts from native earthworms recorded significantly higher functional microbial group's population as compared to the exotic worms. The study reveals that coffee pulp can be very well used as substrate for vermicomposting using exotic (Eudrilus eugeniae) and native earthworm (Perionyx ceylanesis).

Survey on ochratoxin A in Indian green coffee destined for export.

Ochratoxin A (OTA) is a toxic metabolite, produced by Aspergillus spp. and Penicillium verrucosum, that is nephrotoxic and possibly carcinogenic to humans. The aim of this study was to evaluate OTA contamination in batches of green coffee destined for export. Analysis of 80 green coffee samples indicated that, although a high incidence (74%) of OTA contamination (0.2-13.5 ng g⁻¹) was recorded, the overall mean OTA level (2.17 ± 2.45 ng g⁻¹) was low. The highest recorded OTA concentration was 13.5 ng g⁻¹ in a robusta cherry sample and only five samples had OTA above 5 ng g⁻¹ level. The mean OTA level was higher in cherry (range: 1.63 ± 0.97-4.8 ± 3.90) than parchment (0.56 ± 0.35-1.10 ± 0.28), indicating a correlation between processing method and OTA contamination.