Abstract:

This study aims to investigate the effects of Kocuria rosea SDB9 and Brevibacterium frigoritolerans SDB5 on the nutritional quality of rice. Using rice as the experimental material, the seeds were soaked with SDB9, SDB5, and a 1:1 mixture of both strains. The content of nine nutritional components in the rice grains was measured after harvest. The results were as follows. Compared to the control group (CK), the starch content in the experimental groups increased by only 1%, which was not statistically significant; crude protein content decreased by 3%-5%, also was not significant; crude fat content increased in all treatments, with a significant increase of 14.9% in the SDB9+5 treatment; soluble total sugar content decreased by 52.5%-58.3%, which was highly significant; reducing sugar content increased in all treatments except for a slight decrease of 0.6% in the SDB5 treatment, with a significant increase of 25.9% in the SDB9 treatment and an 8% increase in the SDB9+5 treatment, which was not significant; soluble protein content decreased in all treatments, with a significant decrease of 14.9% in the SDB9+5 treatment; cellulose content increased by 0.8%-0.9% in all treatments except for a slight decrease of 0.2% in the SDB9+5 treatment; vitamin C content decreased in all treatments, with a highly significant decrease of 64.5% in the SDB9 treatment and a significant decrease of 16.1% in the SDB5 treatment, while the SDB9+5 treatment showed a significant decrease of 35.5%; nitrate content decreased by 1%-12.8%, with no significant differences observed. In summary, treatment with SDB9 and SDB5 alone or in combination resulted in a slight increase in starch content and an approximate 8% decrease in crude protein content, improving rice palatability. The increase in crude fat and decrease in nitrate levels contributed positively to quality improvement. This indicates that Kocuria rosea SDB9 and Brevibacterium frigoritolerans SDB5 can improve the nutritional quality of rice to some extent. The evaluation of these two strains based on nutritional quality ranked them as follows: SDB9 > SDB9+5 > SDB5 > CK.

Key words: rhizosphere promoting bacteria, Kocuria rosea, Brevibacterium frigoritolerans, rice, nutritional quality