Bacterial biodiversity and optimization of pilot plant-based storage parameters of beet thick juice under Egyptian environmental conditions

In hot-weather regions such as Egypt, where maintaining lower storage temperatures is both economically unfeasible and a significantly difficult, this study was directed towards optimizing the storage of beet thick juice in order to enhance white sugar yield and reduce the impact of climate change. In this study, a pilot plant consisting of 12 storage cylinders was used to maintain thick beet juice with total soluble solids (ºBrix) of 67, 68, and 69 at 15, 25, and 35 ºC, respectively. Betastab® XL (Hop ß-acids) and KEBOCID 310 (sodium dimethyldithiocarbamate) were employed as biocides at 40 ppm. Surface sealing using 25.0% NaOH along with air removal was also applied. The relationships between bacterial count (CFUs), pH, lactic acid (LA) concentration, and reducing sugars (RS) content were evaluated. CFUs increased gradually with the length of the storage period in all tanks, reaching its peak (350 CFU/mL) in the control tank at 35 °C. LA and RS values were determined in all tanks and occurred at very low concentrations. pH exhibited a stable behavior with the exception of the control tank at 35 ºC that displayed degradation correlated to a pH drop to 7.32. Species of bacteria associated with the stored thick juice were isolated and identified by sequencing the 16 S rRNA. These included Bacillus cereus, B. licheniformis, B. paralicheniformis, B. subtilis, Bordetella muralis, Brevibacillus agri, Pseudomonas juntendi, and Stenotrophomonas geniculata. Antibacterial activity of both biocides at three concentrations-20, 40, and 60 ppm-was investigated against the species isolated. Hop ß-acid concentrations showed significant effects on the investigated bacteria with the exception of B. muralis and P. juntendi. All bacteria, with the exception of B. licheniformis AUMC B-550, were significantly affected by KEBOCID 310 concentrations. However, S. geniculata responded negatively to 20 ppm of KEBOCID 310. For the investigated strains, the effects of KEBOCID 310 at 40 and 60 ppm were almost identical. Along with better control over juice solids content and storage temperature, identifying the source and type of the bacterial infection can assist with managing the process and reduce thick juice deterioration. Sugar industry designers could potentially benefit from this study's elucidation of the ideal circumstances for cost-effective storage in hot temperature zones.

Enzymatic saccharification of banana peel and sequential fermentation of the reducing sugars to produce lactic acid

An integral bioprocess to produce lactic acid (LA) from banana peel (BP) was studied. Oxidases produced by Trametes versicolor and hydrolases produced by Aspergillus flavipes and Aspergillus niger saccharified BP at optimal conditions: 230 rpm, 66 g/L BP, and 73.5% (v/v) of enzymatic crude extract (using equal quantities of the enzymatic extracts). At bioreactor scale (1 L), the joint action of oxidases and hydrolases released 18 g/L of reducing sugars (RS) after 24 h (60% corresponded to glucose), consuming the BP polysaccharides. Lactobacillus delbrueckii fermented the released RS, producing 10 g/L of LA; while in the sequential fermentation (inoculating L. delbrueckii after saccharification), 28 g/L of LA were produced, observing an apparent decrease in feedback inhibition of hydrolases below 1.5 g/L of RS. This process is susceptible for upscaling to produce high LA concentrations and represents a platform to utilize agroindustrial wastes to obtain value-added products.