Enhanced chitosan production and modeling hyphal growth of Mucor rouxii interpreting the dependence of chitosan yields on processing and cultivation time

Abstract

Chitosan is a major structural component of fungal cell walls and has diverse medical and other applications. However, cost‐effective culture and extraction methods for fungi need to be developed. Therefore, Mucor rouxii was grown on YPG‐media in both submerged batch and semi‐continuous cultures. Chitosan was extracted from the mycelia to explore strategies to enhance yields and production rates. As observed in earlier studies, M. rouxii is able to adapt to shear stress when cultured semi‐continuously. Modeling the hyphal growth of batch experiments shows that the mycelia were ruptured by shear forces within a short cultivation time shown by a decreased hyphal length. However, an increasing chitosan content was observed with an increasing cultivation period in semi‐continuous cultures, which is an indication for the adaption to shear stress. Semi‐continuous culture resulted in the highest contents of extractable chitosan. The results and models of hyphal growth, including tip extension and branching, suggest that repeated batch cultures may be optimal for chitosan production.

Chitosans from Rhizopus stolonifer (strain CBMAI 1551): Characterization and Dense Film Formation

“…For submerged culture of the strain, we used YPG broth [34] with minor modifications, as follows (in g L All material and ingredients were sterilized by autoclaving (15 min at 121 ºC). Inoculum was made by spores (10 6 .mL -1 ), obtained in YPG agar from Roux bottles [20].…”

“…[34] with smallmodifications, as follows: the acid solution after demineralization was reserved for precipitation of native chitosan (not deacetylated), which was compared with the semi-synthetic chitosan (obtained by deacetylation). Obtained chitosans were identified as: CTS1551ss(semi-synthetic) and CTS1551n (native).…”

“…Although yield of native chitosan forstrain 1551 was from 2.8-3.3 times greater than other studies [17] and [32],it must be noted that different methods of extraction, medium composition, incubation conditions, and different strains were employed for each study. When compared with another Mucorales member(Mucorrouxii),for example, even with the same conditions of incubation and methodology of extraction, yields are far beyond(between 0.8-0.9 % of total chitosanyield -semi-synthetic plus native) [34]. It's important to note that yield is not only directly related to these variables, but also by the species and strain.…”

“…In a Apreviuosly work with R. stoloniferobtained native chitosan with 60,9% of deacetylation by infrared analysis [17]. Mucorrouxii had both chitosans treated as one and the DD obtained was higher (86-88%) [34], but it should be noted that, as a Mucorales, M. rouxxi produces natural chitosan, which, subjected to a deacetylation step, enhances the overall DD. It should be noted that although this can provide a higher final chitosan yield, the process also generates a more heterogenic product, as native chitosan crystallinity, viscosity, molecular range distribution, among other characteristics, are changed when thermo chemical deacetylation, an unquestionably severe process, is employed.…”

“…Thermochemical processes were used for extraction and deacetylation of chitosans [34], but no further purification was employed at this stage. Attention was made for the detection of native chitosan, which was treated separately from the chitosan obtained by deacetylation of chitin.…”