Screening and fermentation optimization of Methylophilus sp. HN238 for efficient microbial protein production using methanol

Abstract

The global demand for large-scale and cost-effective production of high-quality protein has become increasingly urgent, with microbial protein derived from methanol being recognized as a promising solution. Among 50 methylotrophic strains, Methylophilus sp. HN238 was selected for its capability to utilize methanol as the sole carbon. Through optimization of the medium composition, a 387.30% increase in protein yield was achieved during shake-flask fermentation. Subsequent scale-up to a 5 L bioreactor resulted in a protein content of 57.30%. Amino acid composition analysis revealed that 18 amino acids were quantitatively detectable in the protein, with essential amino acids accounting for 44.10% of the total composition, thereby demonstrating compliance with the World Health Organization (WHO) standards for high-quality protein. Transcriptomic differential analysis was conducted to investigate the metabolic response of Methylophilus sp. HN238 to methanol concentrations (10 g/L vs. 50 g/L). It was observed that high methanol concentrations promoted the upregulation of methanol dehydrogenase (MDH) encoded by the maxI gene, while formaldehyde dehydrogenase (FLD) and cytochrome c (cyt c) were downregulated. This regulatory imbalance was associated with intracellular formaldehyde accumulation, impaired electron transport chain efficiency, oxidative stress, and subsequent inhibition of cellular growth. The study not only validated the potential of Methylophilus sp. HN238 for protein production with high methanol concentrations but also provided critical insights into metabolic engineering strategies to enhance methanol-to-biomass conversion efficiency.

Keywords

Methanol / Methylophilus sp. / Microbial protein / Amino acids / Fermentation optimization

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