Chitin/chitosan extraction from shrimp shell waste by a completely biotechnological process.

Two lactic bacteria were used in sequential co-cultures to demineralize (DM) and deproteinize (DP) shrimp shells (SS) to obtain chitin. During the first 24 h, Lactobacillus delbrueckii performed the DM in a minimal medium containing 100 g/L SS and 50 g/L glucose. Then, three different conditions were assayed to complete DM and perform the DP stage: 1) Bifidobacterium lactis was added with 35 g/L of glucose (Ld-G â†’ Bl-G); 2) only B. lactis was added (Ld-G â†’ Bl); and 3) a 35 g/L pulse of glucose was added, and at 48 h, B. lactis was inoculated (Ld-G â†’ G â†’ Bl). The highest DM (98.63 %) and DP (88 %) were obtained using a glucose pulse in the DM step and controlling the pH value above 6.0 in the DP step. Finally, a deacetylases cocktail produced by Aspergillus niger catalyzed the deacetylation of the resulting chitin. The chitosan samples had a deacetylation degree higher than 78 % and a solubility of 25 % in 1.0 N acetic acid. The deacetylation yield was 74 % after a mild chemical treatment, with a molecular weight of 71.31 KDa. This work reports an entirely biological process to get chitin and chitosan from SS with high yields.

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.