Comparative Analysis of the Nutrient Composition of Caulerpa lentillifera from Various Cultivation Sites

doi:10.21203/rs.3.rs-5045026/v1

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Comparative Analysis of the Nutrient Composition of Caulerpa lentillifera from Various Cultivation Sites

https://doi.org/10.21203/rs.3.rs-5045026/v1

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The nutrient, amino acid and fatty acid compositions of Caulerpa lentillifera from various aquaculture regions were assessed to analyze their nutritional characteristics and potential for aquaculture development. The nutrient composition of C. lentillifera was determined according to standard national nutrient determination methods, and the following data were revealed. 1) The basic nutritional components of C. lentillifera were relatively more abundant in the three aquaculture areas in Guangdong Province. The crude protein content was significantly greater in C. lentillifera from the Dapeng and Daya areas of Guangdong Province than those from the Beihai, Dongshan and Nha Trang areas (P < 0.05). Additionally, the crude lipid content of C. lentillifera from the Daya population was significantly greater than those in the samples from the Beihai, Dongshan, and Nha Trang areas (P < 0.05). Furthermore, the total sugar contents in the Daya and Shanwei populations were significantly greater (P < 0.05) than those in the other four populations. 2) The total amino acid (TAA) content of C. lentillifera ranged from 7.05–12.37%, with notable concentrations of the fresh amino acids aspartic acid (Asp) and glutamic acid (Glu). Significant variations in the TAA and essential amino acid (EAA) levels were observed among the cultivation regions (P < 0.05), with the Shanwei population exhibiting the highest TAA content of 12.37% and EAA content of 4.65%, surpassing all other populations except for Guangdong Province (P < 0.05). 3) The fatty acid composition analysis revealed that the total fatty acid (TFA) and unsaturated fatty acid (UFA) levels in the long-stemmed grape fern alga from Daya were 2.400% and 1.048%, respectively, and significantly greater than those in the other populations except for Dapeng (P < 0.05). These results imply that the nutritional quality of the Daya population of C. lentillifera is relatively high.

Caulerpa lentillifera

Nutrient composition

amino acid

fatty acid

Caulerpa lentillifera is a type of green algae (phylum, Chlorophyta; order, Bryopsidales) in the fern algae genus Caulerpa. Its body is bright green, and due to its solid apparatus, stolons and upright branches, which are distributed on symmetrical cysts, its shape resembles a bunch of grapes; thus, C. lentillifera is also known as the sea grape. C. lentillifera is edible (Chen 2021). C. lentillifera are widely distributed in subtropical and tropical areas, and wild C. lentillifera grow in shallow sandy or muddy sandy areas in the high tide and intertidal zones (Tao 2016). Moreover, C. lentillifera is rich in amino acids, unsaturated fatty acids (UFAs), vitamins, minerals and a variety of polysaccharides and it has the advantages of low liquid and low calorie contents but high protein and dietary-fiber contents. Additionally, C. lentillifera has a rich and juicy taste, similar to caviar; thus, it is also known as green caviar (Tong et al. 2022; Xing et al. 2019). Furthermore, C. lentillifera contains a variety of active substances. Studies have shown that its extract has strong antioxidant activity and free radical scavenging capacities; immunomodulatory and antitumor activities; anticoagulant effects; and blood sugar and lipid regulatory properties (You et al. 2022; du Preez et al.2020; Wang et al. 2020).

Owing to its high economic value, the production of wild C. lentillifera cannot meet market demands. Therefore, in recent years, artificial breeding has been introduced in Shandong, Fujian, Guangdong, Hainan, Taiwan and other regions via a variety of breeding modes, including sea culture, land-based culture and pond culture (Zhao 2016; Ye 2018). The growth of C. lentillifera has been a major factor in the development of this species. To investigate the quality of C. lentillifera cultured in different areas, the nutrient composition (moisture, crude protein, crude liquid, ash, mannitol and iodine), amino acid composition, fatty acid composition and mass fractions of C. lentillifera from six culture groups in four regions (Fujian, Guangdong, Guangxi and Vietnam) were determined, and the nutrient compositions were compared to better understand the nutrients in C. lentillifera.

Sample collection

C. lentillifera samples were collected from six farms in Guangdong, Fujian, Guangxi and Vietnam. The sampling locations are shown in Table 1. The collected live C. lentillifera samples were brought back to the laboratory, and the surface adherents were removed by washing with seawater for use in the experiments.

Table 1

Sample collection information
Area	Sampling point	Coordinates
Guangdong Province	Dapeng Bay of Penghu Sea area	114°28'48"E, 22°31'12"N
	Daya Bay of Huizhou	114°31'12"E, 22°34'48"N
	Great Lake of Shanwei	115°34'1"E, 22°49'42"N
Guangxi Province	North Sea	109°3'E, 21°25'48"N
Fujian Province	Dongshan	117°25'48"E, 23°34'48"N
Vietnam	Nha Trang	109°19'12"E, 12°10'48"N

Methods by which the basic nutrient composition was determined

The basic nutrient composition of C. lentillifera was determined according to the standard methods of the Association of Official Analytical Chemists (AOAC 2005). For moisture determination, samples were dried at 105°C for 72 h to determine the moisture. Crude protein were calculated based on a Kjeldahl analyzer (Kjeltec 8400, FOSS, Hoganos, Sweden). For lipid analysis, we employed a Soxhlet apparatus (Soxtec 2055, FOSS, Hoganos, Sweden). Ash levels were determined with a muffle furnace (FO610C, Yamato Scientific Co., Ltd, Japan) at 550°C for 5 h. Additionally, the following methods were used to evaluate the other nutrients: total sugar content (GB/T 15672 − 2009), free amino acid content (GB T30987–2014), crude fiber content (GB/T 5009.10–2003), iodine content (GB 5009.267–2016), mannitol content (SC/T 3405 − 2018), total amino acid (TAA) content (GB 5009.124–2016), and fatty acid content (GB 5009.168–2016).

Analysis of the amino acid composition

The amino acid score (AAS) was calculated via the standard essential amino acid (EAA) model score proposed by the FAO/WHO (FAO/WHO 1973), and the amino acid model of egg protein proposed by the Institute of Nutrition and Food Safety of the Chinese Academy of Preventive Medical Sciences (IFSS) was used to calculate the chemical score (CS) (Duan et al. 2017) and essential amino acid index (EAAI).

Data analysis

There were three parallel treatment groups at each sampling point. The data are expressed as the means ± standard deviations (x̅± SDs). All the data were subjected to one-way analysis of variance (ANOVA) in SPSS 26.0 to determine significance, and differences between groups were analyzed by multiple comparisons via Duncan's method, and P < 0.05 was considered to indicate a significant difference.

Comparison of the C. lentillifera basic nutrient compositions

The basic nutrient compositions of C. lentillifera from different regions are shown in Table 2. The C. lentillifera moisture contents were extremely high, close to 95%, and there was no significant difference between the populations (P > 0.05). The ash determination results revealed that the Nha Trang population had the highest ash content (65.50%), the Shanwei population had the lowest content (22.83%), and the ash contents of the Beihai, Dongshan and Nha Trang C. lentillifera populations were significantly greater than those of the three Guangdong populations (P < 0.05). In terms of crude protein content, the Dapeng population had the highest (18.70%), the Nha Trang population had the lowest (12.53%), and the populations followed the order Dapeng Bay > Daya Bay > Shanwei > Dongshan > Beihai > Nha Trang; additionally, the crude protein contents of the C. lentillifera samples from Dapeng Bay and Daya Bay were significantly greater than the samples from the Beihai, Dongshan and Nha Trang populations (P < 0.05). It was also revealed that the Daya Bay population had the highest crude liquid content (5.10%), and the Shanwei population had the lowest content (3.83%). The crude liquid content of the Daya Bay population was significantly greater than that of the Beihai, Dongshan and Nha Trang populations (P < 0.05). Moreover, the Shanwei population presented the highest total sugar content (32.87%), the Nha Trang population presented the lowest content (18.13%), and the Daya Bay and Shanwei populations presented relatively high total sugar contents, which were significantly greater than those of the other four populations (P < 0.05). The mannitol determination results revealed that the DongShan population presented the highest mannitol content (7.47%), the Dapeng Bay population presented the lowest content (5.30%), and the Shanwei and DongShan populations presented significantly greater mannitol contents than the Dapeng Bay population (P < 0.05). Finally, the iodine content of the Nha Trang C. lentillifera population was significantly greater than that of the other populations (P < 0.05). Among the six C. lentillifera populations, the Guangdong population presented a greater content of basic nutrients and was considered to be better quality than the other three regional populations.

Table 2

Nutritional components of *C. lentillifera* cultivated in different areas as mean percent ± standard deviations (n = 3, dry weight, %)
Cultivation area	Guangdong Province			Guangxi Province	Fujian Province	Vietnam
Cultivation area	Dapeng Bay	Daya Bay	Shanwei	North Sea	Dongshan	Nha Trang
Moisture*	94.47 ± 0.51	94.83 ± 0.23	94.73 ± 0.81	94.87 ± 0.32	94.97 ± 0.35	94.57 ± 0.58
Ash	34.07 ± 1.34^b	25.80 ± 0.70^bc	22.83 ± 0.21^c	57.90 ± 8.84^a	59.60 ± 5.99^a	65.50 ± 7.11^a
Crude protein	18.70 ± 0.36^a	18.57 ± 1.59^a	17.20 ± 1.49^ab	13.57 ± 3.33^bc	14.17 ± 2.75^bc	12.53 ± 1.16^c
Crude liquid	4.57 ± 0.47^ab	5.10 ± 0.36^a	3.83 ± 0.81^b	4.67 ± 0.25^ab	3.93 ± 0.35^b	4.27 ± 0.40^ab
Total sugar	24.00 ± 3.38^b	32.50 ± 4.22^a	32.87 ± 2.59^a	19.93 ± 1.93^bc	20.00 ± 2.01^bc	18.13 ± 2.50^c
Mannitol	5.30 ± 1.15^b	6.17 ± 1.46^ab	7.17 ± 0.49^a	6.57 ± 0.40^ab	7.47 ± 0.25^a	6.07 ± 0.25^ab
Iodine	0.05 ± 0.02^ab	0.03 ± 0.01^c	0.04 ± 0.01^bc	0.04 ± 0.00^bc	0.05 ± 0.01^abc	0.07 ± 0.00^a
Notes: values with different letters indicate significant differences within groups (P < 0.05); * indicates fresh weight.

Analysis of the amino acid composition of C. lentillifera

The amino acid compositions and mass fractions of the different populations of C. lentillifera are shown in Table 3. A total of 17 amino acids were detected in the C. lentillifera samples; notably, tryptophan was not detected. The TAA content of C. lentillifera ranged from 7.05–12.37%, the EAA content ranged from 2.89–4.65%, the nonessential amino acid (NEAA) content ranged from 4.15–7.87%, and the flavor amino acid (DAA) content ranged from 3.52%-5.31%. The most abundant NEAA was aspartic acid (Asp, ranging from 0.80%-1.32%), followed by glutamic acid (Glu, ranging from 0.85%-1.21%). There were no significant differences (P > 0.05) among the TAA, EAA and NEAA contents of the three populations of long-stemmed grape ferns in Guangdong, although the TAA and DAA contents in the Daya Bay and Shanwei populations were significantly greater than those in the Beihai, Dongshan and Nha Trang populations (P < 0.05). Additionally, the EAA contents in the Dapeng Bay and Shanwei samples were significantly greater than those in the Beihai, Dongshan and Nha Trang samples (P < 0.05), while the NEAA contents in the Dapeng Bay, Daya Bay and Shanwei samples were significantly greater than those in the Beihai, Dongshan and Nha Trang samples (P < 0.05). Furthermore, the EAA/TAA ratios of the six populations of long-stemmed grape ferns ranged from 35.87%-41.03%, the EAA/NEAA ratio ranged from 55.93%-69.63%, and the DAA/TAA ratio ranged from 41.00%-50.13%. The EAA/TAA, EAA/NEAA and DAA/TAA ratios of C. lentillifera from Beihai, Dongshan and Nha Trang were approximately 40%, 70% and 50%, respectively, with no significant differences among these three regions (P > 0.05) but all were significantly greater than the corresponding ratios from the Guangdong population (P < 0.05).

Table 3

Amino acid composition of *C. lentillifera* cultivated in different areas as mean percent ± standard deviations (n = 3, dry weight, %)
Amino acid	Guangdong Province			Guangxi province	Fujian province	Vietnam
Amino acid	Dapeng Bay	Daya Bay	Shanwei	North Sea	Dongshan	Nha Trang
Thr*	0.77 ± 0.11^a	0.82 ± 0.11^a	0.81 ± 0.05^a	0.44 ± 0.07^b	0.40 ± 0.16^b	0.49 ± 0.11^b
Val*	0.57 ± 0.09^ab	0.57 ± 0.11^ab	0.68 ± 0.05^a	0.49 ± 0.07^ab	0.45 ± 0.15^b	0.54 ± 0.12^ab
Met	0.12 ± 0.06	0.15 ± 0.03	0.08 ± 0.04	0.12 ± 0.01	0.12 ± 0.04	0.12 ± 0.03
Ile*	0.47 ± 0.10	0.41 ± 0.08	0.51 ± 0.04	0.36 ± 0.06	0.35 ± 0.12	0.42 ± 0.10
Leu*	0.82 ± 0.20	0.78 ± 0.12	0.84 ± 0.06	0.62 ± 0.09	0.58 ± 0.20	0.70 ± 0.16
Phe*#	0.70 ± 0.12^ab	0.71 ± 0.09^ab	0.73 ± 0.04^a	0.48 ± 0.08^c	0.44 ± 0.16^c	0.52 ± 0.12^bc
Lys*	0.59 ± 0.07^ab	0.66 ± 0.10^a	0.63 ± 0.05^ab	0.49 ± 0.08^ab	0.43 ± 0.15^b	0.53 ± 0.14^ab
His*	0.30 ± 0.12^a	0.31 ± 0.03^a	0.35 ± 0.01^a	0.15 ± 0.03^b	0.12 ± 0.05^b	0.16 ± 0.05^b
Asp#	1.21 ± 0.15^ab	1.31 ± 0.19^a	1.32 ± 0.07^a	0.86 ± 0.13^c	0.80 ± 0.30^c	0.96 ± 0.18^bc
Ser	0.48 ± 0.07^ab	0.55 ± 0.07^a	0.51 ± 0.03^a	0.30 ± 0.05^c	0.29 ± 0.12^c	0.34 ± 0.09^bc
Glu#	1.10 ± 0.15^ab	1.18 ± 0.13^ab	1.21 ± 0.06^a	0.94 ± 0.16^ab	0.85 ± 0.28^b	1.05 ± 0.20^ab
Gly#	0.90 ± 0.19^abc	1.16 ± 0.19^a	1.07 ± 0.07^ab	0.81 ± 0.09^bc	0.67 ± 0.24^c	0.79 ± 0.14^bc
Ala#	0.29 ± 0.19^b	0.59 ± 0.11^a	0.60 ± 0.05^a	0.49 ± 0.07^ab	0.45 ± 0.15^ab	0.56 ± 0.12^a
Cys	0.26 ± 0.10^a	0.27 ± 0.04^a	0.23 ± 0.01^a	0.09 ± 0.01^b	0.08 ± 0.02^b	0.08 ± 0.01^b
Tyr#	0.37 ± 0.11	0.37 ± 0.05	0.30 ± 0.02	0.33 ± 0.05	0.31 ± 0.10	0.35 ± 0.09
Arg	0.46 ± 0.06^ab	0.58 ± 0.06^a	0.58 ± 0.03^a	0.44 ± 0.06^ab	0.38 ± 0.14^b	0.46 ± 0.09^ab
Pro	1.78 ± 0.21^a	1.86 ± 0.19^a	1.91 ± 0.14^a	0.38 ± 0.06^b	0.33 ± 0.11^b	0.40 ± 0.09^b
TAA	11.18 ± 1.68^ab	12.27 ± 1.66^a	12.37 ± 0.72^a	7.77 ± 1.15^c	7.05 ± 2.48^bc	8.44 ± 1.75^c
EAA	4.34 ± 0.84^ab	4.41 ± 0.65^ab	4.65 ± 0.32^a	3.15 ± 0.49^bc	2.89 ± 1.02^c	3.47 ± 0.80^abc
NEAA	6.84 ± 0.84^a	7.87 ± 1.01^a	7.73 ± 0.39^a	4.63 ± 0.67^b	4.15 ± 1.45^b	4.99 ± 0.98^b
DAA	4.57 ± 0.53^ab	5.31 ± 0.75^a	5.24 ± 0.25^a	3.90 ± 0.57^ab	3.52 ± 1.21^b	4.23 ± 0.83^ab
EAA/TAA	38.63 ± 1.63^b	35.87 ± 0.51^c	37.57 ± 0.45^b	40.50 ± 0.27^a	41.03 ± 0.21^a	40.87 ± 0.91^a
EAA/NEAA	63.00 ± 4.37^b	55.93 ± 1.29^c	60.10 ± 1.15^b	68.10 ± 0.72^a	69.63 ± 0.57^a	69.23 ± 2.61^a
DAA/TAA	41.00 ± 1.45^c	43.23 ± 0.42^b	42.30 ± 0.62^bc	50.13 ± 0.15^a	49.93 ± 0.29^a	50.10 ± 0.82^a
Notes: * Essential amino acids; # flavor amino acids. The values with different letters indicate significant differences (P < 0.05).

A comprehensive assessment of the amino acid profile in C. lentillifera

The nutritional quality of the C. lentillifera cultivated in six different areas was evaluated according to the EAA evaluation criteria proposed by the FAO/WHO, and the results are shown in Table 4. The AASs revealed that the first C. lentillifera limiting amino acid was methionine (Met) + cystine (Cys), and the second limiting amino acid was isoleucine (Ile); moreover, and the amino acid with the highest score among the six different samples was phenylalanine (Phe) + tyrosine (Tyr). Additionally, the chemical score data revealed that the first limiting amino acid of C. lentillifera from all populations was Met + Cys, while the second limiting amino acid varied among the six regions. The second limiting amino acid of the Daya Bay and Beihai populations was Ile, which was in agreement with the AASs, but the second limiting amino acid of the other four populations was lysine (Lys). The amino acid with the highest chemical score differed among the six regions, as threonine (Thr) gave the highest chemical score in the Guangdong region while Phe + Tyr gave the highest scores in the other three region, which is consistent with the AASs. The highest EAAI was found in the Nha Trang, Vietnam, population among the six regions, while the lowest EAAI was found in Dongshan, Fujian, population.

Table 4

Amino acid scores of *C. lentillifera* cultivated in different areas
Evaluation method	Amino acid	Reference proteins	Guangdong province			Guangxi province	Fujian province	Vietnam
Evaluation method	Amino acid	Reference proteins	Dapeng Bay	Daya Bay	Shanwei	North Sea	Dongshan	Nha Trang
AAS	Thr	250	257.35	276.03	295.53	202.70	177.93	242.70
	Val	310	190.51	192.99	248.29	225.74	197.07	269.28
	Met + Cys	220	127.24	142.49	115.19	96.74	86.03	99.24
	Ile	250	155.98	139.13	185.32	167.37	152.96	207.80
	Leu	440	272.96	262.57	306.43	287.15	257.34	347.42
	Phe + Tyr	380	431.15	458.95	496.58	446.87	385.28	523.61
	Lys	340	198.30	221.06	230.12	224.22	191.16	264.30
CS	Thr	292	88.13	94.53	101.21	69.42	60.93	83.12
	Val	411	46.35	46.96	60.41	54.92	47.95	65.52
	Met + Cys	386	32.96	36.92	29.84	25.06	22.29	25.71
	Ile	331	47.12	42.03	55.99	50.56	46.21	62.78
	Leu	534	51.12	49.17	57.38	53.77	48.19	65.06
	Phe + Tyr	565	76.31	81.23	87.89	79.09	68.19	92.67
	Lys	441	44.96	50.13	52.18	50.84	43.35	59.93
EAAI		100	52.59	54.23	59.65	52.12	45.89	61.09

Analysis of the fatty acid composition of C. lentillifera

The fatty acid compositions and mass fractions of different populations of C. lentillifera are shown in Table 5. A total of 13 fatty acids were detected in C. lentillifera, including four saturated fatty acids (SFAs), three monounsaturated fatty acids (MUFAs), and six polyunsaturated fatty acids (PUFAs). The total fatty acid (TFA), SFA, MUFA, and PUFA contents of the Daya Bay population were significantly different from those of the Shanwei, Beihai, Nha Trang, and Dongshan populations (P < 0.05). Among the 13 fatty acids detected, palmitic acid (ranging from 0.494%-1.068%) and linoleic acid (0.264%-0.392%) had the highest contents, and the contents of these fatty acids were significantly greater in the Daya population than in the other populations (P < 0.05). The ratios of UFAs to TFAs ranged from 42.58%-46.11%, with the highest ratios in the Beihai population and the lowest in the Shanwei population.

Table 5

Comparative analysis of the fatty acid contents of *C. lentillifera* cultivated in different areas as mean percent ± standard deviations (n = 3, dry weight, %)
Fatty acid	Guangdong Province			Guangxi Province	Fujian Province	Vietnam
Fatty acid	Dapeng Bay	Daya Bay	Shanwei	North Sea	Dongshan	Nha Trang
Myristic acids C14:0	0.022 ± 0.003^b	0.042 ± 0.004^a	0.036 ± 0.015^a	0.006 ± 0.002^c	0.009 ± 0.002^c	0.009 ± 0.004^c
Palmitic acids C16:0	0.886 ± 0.097^b	1.068 ± 0.029^a	0.853 ± 0.203^b	0.661 ± 0.055^c	0.537 ± 0.050^c	0.494 ± 0.041^c
Docosanoic acids C22:0	0.049 ± 0.005^a	0.050 ± 0.007^a	0.035 ± 0.006^b	0.028 ± 0.002^bc	0.020 ± 0.004^c	0.019 ± 0.004^c
Lignoceric acids C24:0	0.189 ± 0.019^a	0.192 ± 0.023^a	0.141 ± 0.026^b	0.117 ± 0.011^b	0.082 ± 0.013^c	0.082 ± 0.009^c
ΣSatuurated fatty acids SFA	1.146 ± 0.123^ab	1.325 ± 0.055^a	1.065 ± 0.238^b	0.813 ± 0.069^c	0.648 ± 0.069^c	0.604 ± 0.050^c
Oleic acids (C18:1),n-9*	0.069 ± 0.002^a	0.068 ± 0.004^a	0.071 ± 0.009^a	0.033 ± 0.004^b	0.025 ± 0.003^bc	0.023 ± 0.005^c
Erucic acids (C22:1),n-9*	0.103 ± 0.014^a	0.096 ± 0.034^a	0.075 ± 0.010^ab	0.032 ± 0.009^c	0.021 ± 0.007^c	0.027 ± 0.012^c
ΣMonounsaturated fatty acids (MUFA)	0.079 ± 0.007^ab	0.084 ± 0.002^a	0.063 ± 0.020^bc	0.054 ± 0.006^cd	0.043 ± 0.005^d	0.051 ± 0.003^cd
Linoleic acids (C18:2),n-6**	0.264 ± 0.024^b	0.329 ± 0.011^a	0.256 ± 0.067^b	0.260 ± 0.037^b	0.194 ± 0.017^c	0.155 ± 0.014^c
Cis-8,11,14-eicosatrienoic acids (C20:3),n-6**	0.009 ± 0.001^b	0.013 ± 0.000^a	0.007 ± 0.002^c	0.006 ± 0.001^c	0.004 ± 0.001^d	0.005 ± 0.000^d
Arachidonic acids (C20:4),n-6**	0.075 ± 0.005^b	0.105 ± 0.002^a	0.067 ± 0.017^b	0.055 ± 0.007^bc	0.040 ± 0.003^c	0.038 ± 0.003^c
Cis-11,14,17-eicosatrienoic acids (C20:3),n-3**	0.007 ± 0.001^d	0.008 ± 0.000^cd	0.008 ± 0.001^cd	0.020 ± 0.003^a	0.012 ± 0.003^b	0.011 ± 0.002^bc
Eicosapentaenoic acids (C20:5; EPA),n-3**	0.055 ± 0.004^a	0.049 ± 0.001^a	0.037 ± 0.012^b	0.025 ± 0.003^c	0.017 ± 0.001^c	0.017 ± 0.001^c
Alpha linolenic acids (C18:3),n-3**	0.265 ± 0.029^ab	0.296 ± 0.007^a	0.206 ± 0.060^bc	0.210 ± 0.036^bc	0.153 ± 0.014^cd	0.133 ± 0.017^d
ΣPolyunsaturated fatty acids (PUFAs)	0.846 ± 0.057^ab	0.964 ± 0.053^a	0.727 ± 0.159^bc	0.641 ± 0.089^cd	0.466 ± 0.041^d	0.407 ± 0.037^d
TFA	2.072 ± 0.180^ab	2.400 ± 0.097^a	1.855 ± 0.413^bc	1.507 ± 0.160^cd	1.156 ± 0.115^de	1.062 ± 0.089^e
UFA/TFA	44.64%	43.66%	42.58%	46.11%	44.03%	43.13%
Notes: * Monounsaturated fatty acids; ** Polyunsaturated fatty acids; Values with different letters indicate a significant difference (P < 0.05).

The collection sites of the C. lentillifera samples in this study, which included the regions of Guangdong, Guangxi, Fujian and Vietnam, span a wide range of geographical locations with environmental differences. In addition to moisture, the nutrient contents of the different populations of C. lentillifera were significantly different (P < 0.05). The ash content of the six populations of C. lentillifera ranged from 22.83%-65.50%, which was in agreement with the results of Syakilla et al.(2022), and the ash contents in Guangxi, Fujian and Vietnam were significantly greater than those in the three Guangdong populations, indicating that C. lentillifera could enrich the inorganic ions in the water (Liu et a. 2020). Moreover, the crude protein, crude liquid and total sugar contents of C. lentillifera ranged from 12.53%-18.70%, 3.83%-5.10% and 18.13%-32.87%, respectively, which were comparable to the ranges of 12.5%-14.76%, 0.78%-2.32% and 21.32%-50.71% reported in the study by Syakilla et al. (2022). Furthermore, these values were essentially the same as those reported by Tang et al. (2018) (9.22% crude protein and 0.81% crude liquid) and Wang et al. (2018) (14.9% crude protein and 4.4% crude liquid). The crude protein, crude liquid and total sugar contents of the Guangdong population were greater than those of the Guangxi, Fujian and Vietnam populations, with Daya Bay population being significantly different (P < 0.05) from the Beihai, Dongshan and Nha Trang populations. The growth of long-stem grape fern algae is affected by various factors, such as temperature, light, growth substrate and growth cycle, and the differences in nutrient contents may be related to the cultivation environment, growth area, sampling time and site (Wang et al. 2017). Seaweeds, especially brown algae, are the main raw material sources from which mannitol and iodine are extracted in China (Song 2016). In this study, the mannitol and iodine contents of C. lentillifera ranged from 5.30%-7.47% and 0.03%-0.07%, respectively, which were lower than those of kelp (12.3%-15.1% and 0.36%-0.47%, respectively) (Yao et al. 2016). Thus, C. lentillifera is a suitable food to supplement the mannitol and iodine required by the human body but not suitable for use as a raw material for industrial extraction.

Amino acids are the basic units of proteins, and the protein content and amino acid composition and content of C. lentillifera should be considered when evaluating the nutritional quality of this algae (Xia et al. 2016). In this study, it was revealed that all six populations had the same amino acid composition, which is consistent with other studies on the nutrient composition of C. lentillifera (Wang 2020). When performing a nutritional evaluation, the FAO/WHO ideal protein model recommends that the ratio of EAAs to TAAs should be approximately 40% and that the EAA/NEAA ratio should be greater than 60% (Xia 2022). The amino acid compositions of five of the six regional populations, with the exception of the Daya population, conformed to the ideal protein model, suggesting that C. lentillifera is a high-quality protein source. Among the six regional populations in this study, the highest EAA/TAA and EAA/NEAA ratios were found in the Dongshan regional population, indicating that this population had highest quality protein, and the high contents of the DAAs Glu and Asp in the six populations were the source of the distinctive seaweed flavor of C. lentillifera. The highest DAA/TAA ratio was observed in the Beihai population, which indicated that this C. lentillifera population had the best fresh flavor. The DAA/TAA ratio was the highest in the Beihai population. Moreover, the proline (Pro) contents in the three Guangdong populations were significantly higher than those in the Beihai, Dongshan and Nha Trang populations, which differs from the amino acid contents reported in other studies. These previous studies on the nutrient composition of long-stemmed grape ferns revealed that proline is an osmotic regulator in plants and that environmental stresses cause an increase in the proline content in plants to improve plant resistance (Zhang et al.2023). This study revealed that proline is an osmoregulatory substance in plants. The high proline content of C. lentillifera in Guangdong may be the result of an increase caused by environmental stress factors.

The AAS results revealed that the first limiting amino acid of C. lentillifera was Met + Cys, and the second limiting amino acid was Ile or Lys, which was essentially consistent with the results of the study by Tang (Tang et al. 2018). The EAAI is an indicator for evaluating the nutrient composition of food, and a high EAAI indicates high nutritional value. The EAAIs of the six populations in this study ranged from 45.89 to 61.09, among which the Nha Trang population had the highest EAAI, and thus, the highest nutritional value.

C. lentillifera is low in liquid but rich in fatty acids, with a total of 13 fatty acids detected, including six UFA species, with percentages ranging from 42.58%-46.11%, which are higher than those reported by Wang (2020), who reported values of 37.09% and 36.74%, respectively. Among the six populations in this study, the Daya Bay population presented the highest TFA and UFA contents, which were significantly greater than those of the Shanwei, Beihai, Dongshan and Nha Trang populations (P < 0.05), whereas the Beihai population presented the highest percentage of UFAs. The fatty acid with the highest content was palmitic acid, which is consistent with the composition of seaweeds such as Gracilaria lichenoides and Meristotheca papulosa (Zhu et al. 2020) and the abundance of palmitic acid in nature. In addition to palmitic acid, C. lentillifera is rich in PUFAs, with high contents of linoleic acid and Alpha linolenic acids, ranging from 0.155%-0.329% and 0.133%-0.296%, respectively. Linoleic acids and Alpha linolenic acids are essential fatty acids that cannot be produced by the human body but are important for preventing diseases and health maintenance (Gu et al. 2018). In addition, the contents of arachidonic acids and EPA were high, at 0.038%-0.105% and 0.017%-0.055%, respectively. Arachidonic acid is essential for the development of the human brain and visual nerves and has important physiological activities. Terrestrial plants and animals rarely contain EPA, as it is mainly found in marine organisms, but EPA can reduce cholesterol and triglyceride contents; promote the metabolism of saturated fatty acids in the body, thus reducing blood viscosity and preventing fat deposition in the blood vessel wall; and prevent cardiovascular diseases such as atherosclerosis, cerebral thrombosis, hypertension (Chen et al. 2021) and other cardiovascular diseases (Li et al. 2021).

The results of this study revealed that C. lentillifera is an edible seaweed rich in protein and total sugar but low in fat. It is a natural and healthy food because it is rich in amino acids present in composition ratios in accordance with FAO/WHO recommended standards. Additionally, C. lentillifera contains a relatively high percentage of a variety of UFAs, in addition to iodine and mannitol. In this study, it was revealed that the nutrient composition of C. lentillifera from different cultivation areas varied greatly; however, C. lentillifera from the Daya Bay had the highest nutritive value, which provides a reference for selecting species to be cultivated.

Competing interests
The authors declare no competing interests.

Funding

This research was funded the Hainan Provincial Natural Science Foundation of China (323MS126), Guangdong province Rural Science and Technology Commissioners Project, Guangdong Natural Science Foundation (2019A1515012159), Financial Special Project of the Ministry of Agriculture and Rural Areas (NHYYSWZZZYKZX2020), Central Public-interest Scientific Institution Basal Research Fund, CAFS (2020KX03, 2023TD97), Rural Revitalization Strategy Special Fund Seed Industry Revitalization Project of Guangdong Province (2022SPY02001).

Author Contribution

W.Z.: designing and performing experiments; Y.W.: designing experiments, writing and revising the manuscript; R.X.: collecting samples and statistical analyses; J.T.: reviewing and revising the manuscript; T.L.: collecting samples and statistical analyses; S.C.: collecting samples and statistical analyses.

Acknowledgement

We thank the editor and anonymous reviewers for their comments that helped improve this work.

Data availability

Data are available from the corresponding author upon reasonable request.

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Comparative Analysis of the Nutrient Composition of Caulerpa lentillifera from Various Cultivation Sites

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Abstract

Introduction

Materials and Methods

Sample collection

Methods by which the basic nutrient composition was determined

Analysis of the amino acid composition

Data analysis

Results

Discussion

Conclusions

Declarations

Competing interests
The authors declare no competing interests.

Funding

Author Contribution

Acknowledgement

Data availability

References

Additional Declarations

Status:

Version 1

Comparative Analysis of the Nutrient Composition of Caulerpa lentillifera from Various Cultivation Sites

Status:

Version 1

Abstract

Introduction

Materials and Methods

Sample collection

Methods by which the basic nutrient composition was determined

Analysis of the amino acid composition

Data analysis

Results

Discussion

Conclusions

Declarations

Competing interests The authors declare no competing interests.

Funding

Author Contribution

Acknowledgement

Data availability

References

Additional Declarations

Status:

Version 1

Competing interests
The authors declare no competing interests.