# Screening of Lactic Acid Bacteria and RSM-Based Optimization for Enhancing γ-Aminobutyric Acid (GABA) Accumulation in Orange Juice

## TL;DR

This study identifies and optimizes lactic acid bacteria to boost GABA levels in orange juice, enhancing its nutritional value.

## Contribution

The novel contribution is the RSM-based optimization of fermentation conditions to maximize GABA accumulation in orange juice using specific LAB strains.

## Key findings

- Lcb. paracasei ZY and Lcb. rhamnosus SN12 showed high GABA production and substrate adaptability.
- Optimized conditions increased GABA content to 0.89 g/L, a 39.06% increase over uninoculated juice.
- RSM-based optimization proved effective for enhancing GABA in functional fermented juices.

## Abstract

Inoculated fermentation can enhance the flavor, nutrition, and functionality of juice. The lactic acid bacteria (LAB) are commonly used as starter cultures. This study screened LAB for orange juice fermentation and optimized fermentation factors using response surface methodology (RSM) to improve GABA content in orange juice. A total of 52 LAB strains were screened, and Lacticaseibacillus paracasei ZY (Lcb. paracasei ZY) and Lacticaseibacillus rhamnosus SN12 (Lcb. rhamnosus SN12) presented higher GABA yields and adaptability to substrates. The optimized fermentation factors for GABA enhancement in orange juice were as follows: initial pH of 5.5, fermentation temperature of 37 °C, soluble solids content of 12.0 °Bx, inoculum ratio of Lcb. paracasei ZY to Lcb. rhamnosus SN12 as 1:1, inoculum size of 6 Log CFU/mL, and fermentation time of 96 h. Under these optimized conditions, the GABA content reached 0.89 g/L, representing a 39.06% increase compared to uninoculated orange juice. This indicates that RSM-based optimization is conducive to increasing GABA content in orange juice and provides a scientific basis for the development of GABA-enriched functional fermented juices.