Utilization of Canteen Food Waste through Anaerobic Digestion and Preliminary Characterization of Acid- Producing Bacterial Isolates from Biogas Digester Sludge

Canteen food waste represents a biodegradable feedstock for anaerobic digestion, while biogas digester sludge provides a potential source of microorganisms involved in organic-acid production. This study evaluated five recorded food-waste treatment observations, examined nutrient-response data, and assessed the acid-producing potential of bacterial isolates obtained from digester sludge. Food waste was mechanically shredded, mixed with water to form a slurry, and introduced into an anaerobic digester. Recorded carbohydrate content ranged from 35% to 72%, protein content ranged from 12% to 32%, and daily fuel-use duration ranged from 4 to 10 h. Treatment T2 recorded the longest daily fuel-use duration of 10 h. Bacterial isolates were screened using Carr medium and glucose–yeast extract–calcium carbonate medium, followed by incubation in ethanol-containing medium (5%) at 30°C and 150 rpm for seven days. Based on the recorded titration inputs of 0.3 mL of 0.5 M sodium hydroxide for a 1.5 mL culture aliquot, the calculated titratable acidity was 6.01 g/L, expressed as acetic-acid equivalents, corresponding to 0.60% (w/v). Assuming an initial concentration of zero, the apparent average productivity over seven days was 0.86 g/L/day. Statistical analysis of the five treatment observations showed positive associations between carbohydrate content and fuel-use duration (\(r = 0.452\)) and between protein content and fuel-use duration (\(r = 0.314\)). In the nutrient-response dataset, the highest recorded response was 1.70 for treatment N5. These findings provide preliminary quantitative information for further investigation of food-waste digestion, nutrient optimization, and microbial acid production.