Optimization of protease production by Bacillus cereus HMRSC30 for simultaneous extraction of chitin from shrimp shell with value-added recovered products

Abstract

Chitin extraction from shrimp shell powder (SSP) using protease-producing microbes is an attractive approach for valorizing shrimp shell waste because it is simple and environmentally friendly. In this study, the protease production and chitin extraction from SSP by Bacillus cereus HMRSC30 were simultaneously optimized using statistical approaches. As a result, fermentation in medium composed of 30 g/L SSP, 0.2 g/L MgSO 4 · 7H 2 O, 3 g/L (NH 4 ) 2 SO 4 , 0.5 g/L K 2 HPO 4 , and 1.5 g/L KH 2 PO 4 (pH 6.5) for 7 days maximized protease production (197.75 ± 0.33 U/mL) to approximately 1.64-fold compared to unoptimized condition (126.8 ± 0.047 U/mL). This level of enzyme production was enough to achieve 97.42 ± 0.28% deproteinization (DP) but low demineralization (DM) of 53.76 ± 0.21%. The high DM of 90% could be easily accomplished with the post-treatment using 0.4 M HCl and acetic acid. In addition, the study evaluated the possible roadmap to maximize the value of generated products and obtain additional profits from this microbial process. The observation showed the possibility of serving crude chitin as a bio-adsorbent with the highest removal capacity against Coomassie brilliant blue (97.99%), followed by methylene blue (74.42%). The recovered protease exhibited the function to remove egg yolk stain, indicating its potential for use as a detergent in de-staining. The results corroborated the benefits of microbial fermentation by B. cereus HMRSC30 as green process for comprehensive utilization of shrimp shell waste as well as minimizing waste generation along the established process.

Chitin, Chitosan, and Nanochitin: Extraction, Synthesis, and Applications

“…Some species of lactic acid-producing bacteria possess lackluster deproteination capabilities; fermentation with protease-producing cultures can follow to improve the purity of produced chitin [ 54 , 55 , 56 ]. Protease-producing bacteria alone rarely provide adequate demineralization and often require an additional demineralization step [ 55 , 56 , 57 , 58 ].…”

“…Fermentation methods of chitin extraction require the preparation of media to support culture growth. The medium may be a complicated mixture of reagents to achieve optimal chitin extraction [ 58 ]. Independent of optimization, all media require a source of carbon for the bacteria to convert into acid; glucose is a common selection for small-scale experiments [ 10 , 13 ].…”

“…As with the enzymatic methods, the supernatant generated by fermentation carries valuable amino acids [ 58 ]. Biological extraction processes are summarized in Table 4 .…”

Simultaneous Preparation of Chitin and Flavor Protein Hydrolysates from the By-Products of Shrimp Processing by One-Step Fermentation with Lactobacillus fermuntum

“…According to the literature, in this case, that is, if LAB are used, the DM and DP have a negative relationship, and the DP rate is usually low because the change in protease configuration under acidic pH environment could affect its activity. Conversely, if proteolytic bacteria are used, the DM rate is low [22,23]. However, as was shown in Figure 1c, the % DM and % DP both increased with elevated initial fermentation pH, increasing from 3.0 to 4.0, whereas they remained constant when the fermentation was started at pH 4.0 through 7.0.…”