Lycium barbarum polysaccharides (LBPs), as bioactive compounds extracted from L. barbarum L. fruit, have been widely explored for their potential health properties. The extraction and structural characterization methods of LBPs were reviewed to accurately understand the extraction method and structural and biological functions of LBPs. An overview of the biological functions of LBPs, such as antioxidant function, antitumor activity, neuroprotective effects, immune regulating function, and other functions, were summarized. This review provides an overview of LBPs and a theoretical basis for further studying and extending the applications of LBPs in the fields of medicine and food.

Lactobacillus brevis CD0817, a strain isolated from a healthy adult gut, was currently the most efficient lactic acid bacterial cell factory for gamma-aminobutyric acid. In this study, the complete genome sequence of CD0817 was determined and compared with some related L. brevis genomes. The CD0817 genome consists of one 2,990,570-bp chromosome and four plasmids. The comparative genomic and phylogenetic analysis revealed that L. brevis CD0817 was not very conserved with low GABA-producing L. brevis strains. A significant divergence was that CD0817 harbors only the gadCA operon whereas the low GABA-producing L. brevis strains contain the operon and gadB . The gadB seemed to only marginally contribute to the accumulation of GABA. The high GABA production ability of CD0817 may be associated with its extraordinary genome. Electronic supplementary material The online version of this article (10.1186/s13568-019-0799-0) contains supplementary material, which is available to authorized users.

Peptides derived from food proteins have exhibited significant antihypertensive effects without side effects. In this study, the cottonseed protein was hydrolyzed by papain for preparing peptide with angiotensin I converting enzyme (ACE) inhibitory activity. The influence of hydrolysis temperature (33°C, 40°C, and 47°C), pH (6.5, 7.0, and 7.5), and enzyme to substrate (E/S) ratio (0.9%, 1.2%, and 1.5%) on the degree of hydrolysis (DH) and ACE-inhibitory activity were analyzed. The hydrolysis conditions were further optimized by central composite design (CCD) and response surface methodology (RSM). The DH of cottonseed protein and ACE inhibitory rate of hydrolysates reached 25.7% and 88.2%, respectively, under the optimal hydrolysis conditions (hydrolysis temperature 39°C, pH 7.5, and E/S ratio 1.04%). We further separated the cottonseed protein hydrolysates (CPH) using a combined strategy of ultrafiltration membrane bioreactor system, sephadex G-25 gel filtration chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC). An ACE inhibitory peptide, named as FII-2-P, with ACE inhibitory IC 50 value of 46.7 μg/mL, was obtained. MALDI-TOF-TOF mass spectrometry analysis revealed that the molecular weight of FII-2-P was 763.4 Da and its amino acids sequence was Phe-Pro-Ala-Ile-Gly-Met-Lys. These results demonstrated that the cottonseed protein is a potential source of ACE inhibitory ingredients to be used in the development of functional foods.

Chicken plasma protein hydrolysate (CPPH) was prepared by trypsin with angiotensin I‐converting enzyme (ACE) inhibitory activity of 53.5% ± 0.14% and the degree of hydrolysis (DH) of 16.22% ± 0.21% at 1 mg·ml−1; then, five proteases, including pepsin, trypsin, papain, alcalase, and neutrase, were employed to improve ACE inhibitory ability by catalyzing plastein reaction. The results indicated that trypsin‐catalyzed plastein reaction showed the highest ACE inhibitory activity. The exogenous amino acids of leucine, histidine, tyrosine, valine, and cysteine were selected to modify the CPPH. The leucine‐modified plastein reaction released the highest ACE inhibitory activity. The effects of four reaction parameters on plastein reaction were studied, and the optimal conditions with the purpose of obtaining the most powerful ACE inhibitory peptides from modified products were obtained by response surface methodology (RSM). The maximum ACE inhibition rate of the modified hydrolysate reached 82.07% ± 0.03% prepared at concentration of hydrolysates of 30%, reaction time of 4.9 hr, pH value of 8.0, temperature of 40°C, and E/S ratio of 5,681.62 U·g−1. The results indicated that trypsin‐catalyzed plastein reaction increased ACE inhibitory activity of chicken plasma protein hydrolysates by 28.57%.

Hypertension was characterized by elevated arterial pressure and contributed an important role on the progression of cardiovascular disease.It was regarded as an "invisible killer" and affect the health of the people (Kuba et al., 2005). Angiotensin I converting enzyme (ACE) was a critical enzyme in the renin-angiotensin system, which could affect the level blood pressure. Many studies have already demonstrated that